Stone Mining and Quarrying (United States)

A Histometrics investor primer · NAICS 2022 code 21231 — the rollup of four child industries

NAICS (North American Industry Classification System) code 21231 is the federal "industry" that groups together every U.S. operation that mines stone from the ground — whether the product is a cut block or crushed rock. It sits inside Sector 21 (Mining, Quarrying, and Oil and Gas Extraction) → Subsector 212 (Mining except Oil and Gas) → Industry Group 2123 (Nonmetallic Mineral Mining). This primer synthesizes the four child-industry primers beneath it and is written for both public-market investors (listed producers, materials and infrastructure funds) and private investors (family/private-equity operators and owners of mineral and royalty rights). Figures are U.S.; data vintages are noted throughout.

The one idea to carry through this primer. 21231 looks like a single "stone" industry, but it is really two very different businesses stapled together. About 96% of it is the construction-aggregates business — cheap, heavy crushed rock whose economics are set by freight, not by a national price, making each quarry a local price-setter. The other ~4% is dimension stone — high-value cut blocks and slabs whose economics are set by provenance and import competition, with no aggregates-style local monopoly and no public pure-play. One code, two cost curves, two ownership worlds, two ways to invest. [1][2][5]

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1. Overview

Stone mining is the largest single piece of the U.S. nonmetallic mineral complex by tonnage. In 2022 the industry generated $17.72 billion of receipts across 969 firms, and in 2023 it ran 2,440 quarries and plants employing 43,124 people with a $3.41 billion payroll — roughly $79,000 of pay per worker, well above the private-sector average, reflecting skilled, capital-heavy blue-collar work. [2][3]

The reason an investor should care is that stone, uniquely among "commodities," is largely immune to the price-crash cycle that governs oil, gas, and metals — and largely immune to the energy transition. Roads, foundations, concrete, rail beds, grids, and data centers all consume rock regardless of the energy mix. But the industry is not one bet; it is a spectrum:

• The crushed-stone trio (limestone, granite, other) — ~96% of receipts — is a freight-protected, local-pricing infrastructure business. Prices are sticky and rise almost every year, even in recessions; the cycle shows up in volumes, not a collapsing headline price. This is where nearly all the public-market investability lives. [5][8][9]
• Dimension stone — ~4% of receipts — is a small, private, provenance-and-freight niche with no exchange price, thin margins, ~81% import reliance, and no listed pure-play. [6]

Ways in.

• Public markets: a handful of listed aggregates producers — most cleanly Vulcan Materials and Martin Marietta — plus diversified global building-materials groups, niche royalty/land companies, and broad materials or infrastructure funds. There is no pure-play stone-mining exchange-traded fund (ETF), no listed dimension-stone company, and no aggregates royalty/streaming company. [8][9][14]
• Private markets: direct or private-equity (PE) ownership of a fragmented long tail of operators, and ownership of the mineral and royalty rights under a quarry (a per-ton royalty as rock is extracted). [12][13][25]

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2. What's inside — the four child industries, and how they differ

21231 contains four child industries. The federal boundary that separates them is two variables at once — the rock type and the product form (cut vs. crushed). The table below is the heart of this primer: it is where the children genuinely diverge.

The contrast table

*Share of group by 2022 Economic Census receipts and 2023 County Business Patterns employment. Rows may not sum to 100% due to rounding. Sources: [2][3][4][5][6].

The five contrasts that matter

1. Relative size. Limestone alone is ~60% of the group; the two other crushed codes add another ~36%; dimension stone is a rounding error at ~4% of revenue. But note the mismatch: dimension stone is ~4% of revenue yet ~11% of employment — it is far more labor-intensive per dollar than crushed rock, because cutting, handling, and inspecting saleable blocks is hand-work, not high-throughput crushing. [4][5][6]

2. Commodity and cost curve. The three crushed children share one economic model — a heavy, ~$18–23/ton product that cannot travel far, so each quarry is a local price-maker with a ~50% cash gross margin at the majors. Dimension stone is the odd one out: no exchange price, no cost-curve benchmark, thin margins, and value driven by color/grain/provenance and by whether cheaper imported slab is available. [5][6][8][9]

3. Price and demand direction. All four are cyclical to construction, but they cycle differently. The crushed trio's volumes soften while unit prices keep rising — average crushed-stone value climbed from ~$12.69/ton (2020) to ~$18.50/ton (2025e). Dimension stone's tonnage has drifted down for years while value held on richer mix; it also faces a headwind the crushed trio does not — ~81% net import reliance, so cheap Brazilian, Indian, Chinese, and Italian slab is a permanent competitive lid. [5][6]

4. Concentration. This is the sharpest structural contrast. Limestone (HHI 287), other crushed (285), and dimension stone (167) are all nationally fragmented; crushed granite is moderately concentrated (HHI 1,666) because the aggregates majors dominate the narrow set of firms whose primary code is granite-crushing. (HHI — the Herfindahl-Hirschman Index — is a 0–10,000 concentration score; below 1,500 is "unconcentrated.") [2][4][5][6]

5. Ownership and access. The crushed trio is where public money can play — via Vulcan, Martin Marietta, CRH, and peers. Dimension stone is private ground: one PE-backed consolidator (Polycor), a few large families (Coldspring), and a long tail of single-quarry operators — no U.S.-listed pure-play has existed since 2016. [6][8][9][13]

A note on the codes' boundaries. All four capture extraction only. The downstream, higher-value manufacturing steps — sawing and polishing slab into countertops and tiles (NAICS 327991), or burning limestone into cement/lime (327310/327410) — sit in other codes and are not in 21231. So company "aggregates" segments (which blend crushed stone with sand and gravel) are broader than 21231, while federal 21231 business statistics are narrower than a vertically integrated producer. Keep the frames labeled. [1]

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3. How big it is

Two federal yardsticks measure two different universes. Both are correct; keep them separate.

3a. The business (U.S. Census Bureau — our ground truth for 21231)

CBP (County Business Patterns) is the annual employer-business series (counts, employment, payroll — no revenue); the Economic Census is the five-year revenue benchmark. Our ingested ground truth for 21231 provides these seven figures — but not a group-level physical tonnage, reserve total, unit value, or per-industry SBA size standard, because those are not defined at this level. Where this primer needs physical or price data it draws on the U.S. Geological Survey commodity series (§3b), and says so.

The rollup is internally consistent. Because every establishment carries exactly one primary code, the children's 2023 CBP figures sum cleanly to the parent: 379 + 1,376 + 251 + 434 = 2,440 establishments; 4,660 + 25,735 + 5,670 + 7,059 = 43,124 employees; and payrolls sum to ~$3.41 billion. The 2022 receipts likewise reconcile: $770M (dimension) + $10.585B (limestone) + $3.12B (granite) + $3.246B (other) ≈ $17.72 billion. One honest exception: firm counts do not add up — the four children list 1,043 firms but the parent shows only 969, because a single firm operating in more than one child industry is counted once at the parent level. [2][3][4]

National concentration is low. The Economic Census puts the four largest firms at 32.0% of group revenue (CR4), the top 8 at 40.4%, the top 20 at 52.4%, and the top 50 at 66.6%, with an HHI of 340.7 — far below the 1,500 "unconcentrated" line. That low group HHI is driven by limestone's weight: even though crushed granite is moderately concentrated on its own, the fragmented limestone majority dominates the blend. Nationally this is a fragmented industry; it only looks concentrated locally (see §8). [2]

3b. The physical commodity (U.S. Geological Survey — the authoritative volume/value measure)

The USGS (U.S. Geological Survey, the federal agency that tracks nonfuel mineral production) reports by rock type and product, not by NAICS code, so its universe does not line up one-to-one with 21231 — but it is the only source for tonnage, unit value, reserves, and trade.

Source: USGS Mineral Commodity Summaries 2026. [5][6]

Two facts jump out. First, dimension stone is ~10× the unit value of crushed stone but ~1/650th the tonnage — it is a high-value sliver by weight. Second, USGS's ~$27 billion crushed-stone value sits well above the ~$17 billion of Census receipts for the three crushed children — not a contradiction, but different universes: USGS counts crushed-stone quarries of every rock type (including quarries captive to cement or concrete plants classified elsewhere), while Census counts only establishments whose primary activity is the code, in an earlier year. [2][5]

Reserves. USGS calls U.S. stone reserves "adequate" and resources "plentiful," and publishes no numerical national reserve tonnage for any of these codes. For the crushed trio the binding scarcity is not geology but permitted rock within economical haul distance of a growing market; for dimension stone it is the specific marketable, permitted deposit (color, grain, intact-block recovery), not rock in general. Trade differs sharply too: crushed stone is essentially domestic (net import reliance ~1%), while dimension stone is ~81% import-reliant by value. [5][6]

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4. The investable universe

Because listed companies' "aggregates" segments blend crushed stone with sand and gravel (and, for the diversified names, cement, foreign operations, and downstream products), the names below describe investable companies, not clean shares of any 21231 child. Every one is leveraged to construction volumes and local pricing, not to a fungible national stone price. This section — and only this section, plus §10 — carries tickers, yields, and valuation shorthand. Market caps are approximate mid-2026 figures, not federal statistics, and move with the market.

Public producers — the crushed-stone trio (~96% of the group)

Note: Summit Materials is no longer public — Quikrete completed a ~$11.5 billion take-private in February 2025, shrinking the listed universe further. [12]

Dimension stone (~4% of the group) — no public pure-play

There is no U.S.-listed dimension-stone producer. The last one, Rock of Ages, went private in 2016. Public investors can touch the theme only obliquely — through the aggregates majors above (different economics), or through Caesarstone (Nasdaq: CSTE), an engineered-quartz maker that is a manufactured substitute for natural stone and therefore a contrarian/substitution angle, not a proxy. [6]

Royalty / land vehicles (niche, aggregates-tilted)

Unlike precious metals (Franco-Nevada, Wheaton), there is no large pure-play stone royalty/streaming company. The nearest listed exposures are FRP Holdings (Nasdaq: FRPH) — a real-estate company with a genuine aggregate mining-royalty segment (per-ton royalties on tons × price) — and Natural Resource Partners (NYSE: NRP), a mineral-rights partnership where aggregates are a small slice. [14][24]

Funds

No U.S.-listed ETF is a pure aggregates play, let alone a stone-mining play. The nearest are XLB (Materials Select Sector SPDR — held VMC/CRH/MLM at ~4.5–4.7% each in mid-2026, but construction materials were only ~14% of the fund) and infrastructure funds PAVE and IFRA (which also hold machinery, engineering, and steel). Check weights at the investment date. [28]

Major private, family, and foreign owners (where much of the real tonnage sits)

• Crushed trio: Quikrete (private; a top-tier owner overnight via Summit); Rogers Group (largest privately held U.S. aggregates producer — ~13 states, ~86 quarries, ~3,500 employees); Luck Stone / Luck Companies (multigenerational family); Blue Water Industries (PE consolidation platform); New Enterprise Stone & Lime, NEBCO, H&K Group; and foreign strategics CRH, Heidelberg Materials, Cemex, Amrize (ex-Holcim), Carmeuse. A Martin Marietta management estimate puts roughly 67% of U.S. aggregate production in private hands, 33% public — a management figure for all aggregates, not an official statistic. [12][13][25]
• Dimension stone: Polycor Inc. — the North American consolidator (self-described world's largest natural-stone quarrier; ~50 quarries), which rolled up Swenson Granite, Rock of Ages, and Indiana Limestone, backed successively by Wynnchurch Capital and then Birch Hill Equity Partners / Investissement Québec; Coldspring (family-controlled since 1898, ~30 quarries); and Vermont Quarries (Danby marble, taken to full Italian ownership by RED Graniti in 2025). [6][13]

No federal dataset quantifies the family/PE/foreign/public ownership split at any of these codes — precise percentages would be speculative.

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5. How the money works

Stone is a commodity by product but — for ~96% of the group — a local-pricing business by economics. Here is where the children converge and where they split.

The crushed-stone trio: freight-limited local pricing (the shared model)

Crushed stone is low-value and high-weight, so transport frequently runs 30–70% of the delivered cost, and the economics break down beyond roughly 25–50 miles of trucking. Vulcan reports ~80% of its shipments move by truck straight from quarry to customer. Within a quarry's haul radius, permitting barriers and scarce sites mean few substitutes — a structural local monopoly or tight oligopoly. Two consequences define the investment case:

1. Local pricing power. No distant competitor can ship rock in cheaply, so each quarry is closer to a price-maker than a global price-taker. Aggregate prices have risen almost every year, including through recessions. [5][8][9]
2. Barriers are locational and regulatory, not geological. The scarce asset is a permitted quarry near where construction is happening — abundant unpermitted rock is nearly worthless; a permitted reserve in the path of growth is the crown jewel. [5][8]

There is no national break-even comparable to oil's lifting cost or gold's AISC (all-in sustaining cost, the metals cash-cost benchmark). The relevant framework is price, cash cost, and gross profit — per ton. Vulcan's 2025 figures illustrate the whole trio's economics: ~$21.98/ton freight-adjusted price − ~$10.65/ton cash cost ≈ $11.33/ton cash gross profit (~51% cash margin) — extraordinary for anything labeled "mining," and a direct product of local pricing plus operating leverage (fixed plant and permits mean each extra ton is highly profitable). The striking feature: pricing has run counter to volume — as shipments dipped in 2024–25, freight-adjusted price kept rising. That margin resilience is the core of the case. [8][9]

Reserves, depletion, capital. Reserve lives are long (Vulcan ~70+ years, Martin Marietta ~85), so reserve-replacement urgency is low versus oil and gas. Depletion is a non-cash tax shield: U.S. law allows 5% percentage depletion for stone sold as construction aggregate/road base/riprap/ballast, rising to 14% for certain specialty chemical/metallurgical uses. Capital intensity is real but manageable — crushers, screens, and haul fleets are expensive and long-lived — producing high, stable free cash flow once a quarry is developed. Operators either own the land (Vulcan ~63% of reserves) or lease it and pay a per-ton or percentage royalty (Vulcan paid ~$128.6M in 2025, ~$0.57/ton company-wide). [8][9][21]

Dimension stone: the exception inside the group

Dimension stone (~4%) breaks the model. There is no exchange price and no standardized grade — a quarry's revenue is saleable-block volume × realized price, where price depends on color, grain, block size, finish, and architectural specification. Block recovery is its "ore grade": a deposit can hold vast rock while yielding few intact, correctly colored, commercially sized blocks, and off-spec rock migrates down into the low-value aggregate stream. There is no AISC benchmark and no finding-and-development (F&D) cost series for this fragmented private niche; margins are thin, operating leverage high, and the competitive lid is imported slab (~81% net import reliance). Its depletion allowance runs 14% (7.5% for slate used as lightweight aggregate; 5% for rubble). [6]

The common thread

Neither business gives clean "commodity beta." The crushed trio is cyclical in volume, sticky in price; dimension stone is cyclical in both volume and realized price, plus import-exposed. Neither is exposed to WTI (West Texas Intermediate crude), LNG (liquefied natural gas), steel, or EV/critical-minerals super-cycles. And neither is a regulated utility or a REIT — there is no rate base and no funds-from-operations story here; the right lens is reserves, per-ton margin, royalties, and depletion. [5][6]

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6. What drives demand

Demand across all four children is derived from construction, but the mix differs.

Crushed trio (~96%). USGS puts 2025 crushed-stone end uses at ~72% construction aggregate (mostly roads), 17% cement, 6% lime, 1% agriculture, 4% other. The demand stack:

1. Public infrastructure — the swing factor. Roads and bridges are the largest single market; the Infrastructure Investment and Jobs Act (IIJA, 2021) put ~$350 billion into federal highways through fiscal 2026 — now in peak spend-out, with reauthorization the key medium-term catalyst-and-risk. [5][20]
2. Private nonresidential / reshoring — warehouses, data centers, semiconductor and battery plants, and grid build-out, which USGS flags as 2026 demand support and which are largely independent of the housing cycle. [5]
3. Residential — interest-rate-sensitive; soft housing weighed on 2024–25 volumes.
4. Specialty: railroad ballast is a signature 212319 (traprock) market; cement/lime feedstock is more a 212312 (limestone) story; aglime is a small non-cyclical slice. [5]

Dimension stone (~4%). A different, more consumer-discretionary stack: residential construction and remodeling (countertops, flooring, facing — the dominant driver, tied to housing starts and rates), nonresidential/institutional facades, monuments and memorials (a stable niche facing a secular headwind as the U.S. cremation rate passed ~63% in 2025), and restoration/historic matching (a defensive, price-inelastic moat for legacy quarries). [6][27]

Long-run, all four track population, urbanization, and the built-environment stock; short-run they track interest rates, weather, and the federal highway-funding cycle. [5]

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7. Regulation

Regulation is nearly identical across the four children — and for the crushed trio it functions as a moat as much as a cost.

• MSHA (Mine Safety and Health Administration) regulates every quarry as a metal/nonmetal mine — mandatory inspections (surface mines at least twice a year), training (30 CFR Part 46), blasting rules. Safety is relatively good: 2024 total-recordable injury rates run ~1.8–1.9 per 100 workers across the codes; BLS (Bureau of Labor Statistics) recorded 3 fatalities in limestone (212312) in 2024. The live issue is the respirable crystalline silica rule: MSHA's April 2024 final rule halved the permissible exposure limit (PEL) to 50 µg/m³, but after an 8th Circuit stay the metal/nonmetal compliance date was delayed indefinitely — dust-control capital remains prudent (granite and quartzite are quartz-rich, so it bites hardest in 212313/212319), but the deadline is unsettled. [16][17][22]
• EPA (Environmental Protection Agency) and states. Clean Air Act dust standards (40 CFR Part 60 Subpart OOO) govern crushers and conveyors; Clean Water Act NPDES (National Pollutant Discharge Elimination System) permits and §404 wetlands rules cover dewatering and stormwater (40 CFR Part 436 explicitly covers crushed stone; the dimension-stone effluent subpart is reserved). State and local zoning is the binding constraint on new supply — and USGS repeatedly warns that zoning pushes quarries away from cities, creating regional shortages and above-average urban price increases. What blocks new entrants protects incumbents' pricing. [18][19]
• BLM (Bureau of Land Management) / federal land — minor here. Most quarrying is on private or state land. Since 1955, "common variety" stone on federal land is sold as a saleable mineral material at fair market value under the Materials Act, not located as a mining claim under the General Mining Law of 1872 — so there is no oil-and-gas-style federal leasing or production-royalty regime for stone. [18]
• Taxes and trade. State severance, property, and sales taxes vary; no uniform national rate. The one place trade policy matters is dimension stone: because the U.S. is ~81% import-reliant, tariff escalation on Brazilian/Indian/Chinese/Italian stone is a direct tailwind for domestic dimension quarries — while the crushed trio (net import reliance ~1%) is essentially untouched. [5][6]
• ESG. Lower-profile than coal or oil: land disturbance, dust, silica, blasting, and reclamation, but no tailings chemistry or acid-mine drainage. The carbon-intensive step is the downstream cement/lime kiln, so decarbonization pressure lands on the cement-bound ~17% of limestone, not on the aggregate-bound majority. [5][19]

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8. Consolidation

Fragmented nationally, concentrated locally — and consolidating. The apparent contradiction between "969 firms, HHI 341" (§3) and "local monopoly" (§5) is resolved by freight: Vulcan estimates ~5,000 companies run ~11,000 U.S. aggregate facilities, with the ten largest at only ~35% of national output — yet a given town may have only two economically deliverable quarries. That is why the FTC (Federal Trade Commission) and DOJ (Department of Justice) analyze deals market-by-market (CRH's Ash Grove deal required three quarry divestitures in one Kansas county; Vulcan's Aggregates USA deal forced 17). [2][5][23][26]

Consolidation is the dominant secular theme across the crushed trio, because buying permitted reserves is faster and often cheaper than permitting new ones. Recent deals: Quikrete–Summit (~$11.5B take-private, 2025); Martin Marietta–Blue Water ($2.05B, 2024) and its Quikrete asset exchange (2026); pending CRH–Arcosa (~$8.5B) and Martin Marietta–Lhoist (~$13.5B). In dimension stone, consolidation is real but slow and entirely private — Polycor's roll-up (Swenson, Rock of Ages, Indiana Limestone) under successive PE owners is the clearest thread, with company counts drifting from ~200 to ~150 over 2021–2025. The risk in both worlds is overpaying for reserve tons that cannot be profitably delivered — cheap rock without permits, access, quality, or nearby demand is expensive. [6][8][9][12][13][23]

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9. Risks

1. Commodity-price / construction cyclicality — the central risk, but muted on price. For the crushed trio (~96%), "commodity-price risk" is really local price–volume–cost-spread risk, and the volume leg (tied to highways, housing, and nonresidential work) moves far more than the price leg, which the freight moat keeps from collapsing — a genuinely gentler cycle than oil, gas, coal, or metals. For dimension stone (~4%), both volume and realized price cycle, and there is no benchmark or futures contract to hedge either. [5][6][8]
2. Infrastructure-funding cliff. IIJA highway authorization runs through fiscal 2026; a delayed or smaller reauthorization would remove a key demand pillar for the crushed trio. (Already-obligated funds keep flowing, so a lapse would not halt work immediately — but it is a live overhang.) [5][20]
3. Cost inflation. Diesel, electricity, labor, explosives, steel wear parts, and freight can outrun price increases; the model depends on pushing price faster than cost (achieved recently, not guaranteed). [8][9]
4. Permitting, zoning, silica, and reclamation. The same local opposition that protects incumbents constrains their own expansion; the silica rule (if reinstated) raises cost, hardest for quartz-rich granite/quartzite; reclamation is a long-tail liability. [16][17][19]
5. Import competition — dimension stone only. ~81% net import reliance means domestic dimension quarries are perpetually undercut by cheaper foreign slab; a strong dollar worsens it. The crushed trio is immune (import reliance ~1%). [6]
6. Substitution. Engineered quartz, large-format ceramic, and recycled concrete/asphalt erode natural-stone and virgin-aggregate share at the margin. [5][6][15]
7. Localized reserve depletion / sterilization. The danger is not running out of stone nationally but exhausting a well-located quarry and being forced to haul farther — a margin risk, not a solvency risk, given multi-decade reserve lives. [5][8]
8. Acquisition and leverage risk. The best permitted portfolios command high prices; overpayment, debt-funded mega-deals, and integration missteps can destroy otherwise strong site economics. [8][9][23]
9. Illiquidity and concentration — private owners. Especially in dimension stone, assets are closely held with no public market, and the anchor base sits with a single PE-backed owner. [6][13]
10. Energy-transition / stranded-asset risk — LOW (a relative strength). Unlike coal or oil, stone faces little demand destruction from decarbonization — roads, grids, renewables, and data centers all consume rock, and dimension stone markets a low-embodied-carbon "100-year material" narrative. The only carbon exposure is indirect (diesel/freight) and, for integrated producers, cement. This is a key differentiator from the fossil-fuel corners of Sector 21. [5][6][19]

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10. How to invest, and outlook

Public routes (essentially all crushed-stone / aggregates)

• Producer equities give leverage to local price increases, volume recovery, fixed-cost absorption, reserve appreciation, and accretive M&A — not to a fungible stone price. Vulcan (VMC) and Martin Marietta (MLM) are the liquid pure-play large-caps; CRH, Amrize, Knife River, Arcosa, Eagle Materials, and Titan America offer broader building-materials exposure. None is a stone-only play, and none touches dimension stone. [8][9][10][11]
• Return character — NOT the oil/metals boom-bust. Because the product price does not crash, capital returns are steady and growing rather than feast-or-famine: these are compounders, not high-yielders (VMC ~0.7%, MLM ~0.5% dividend yield). In 2025 each paid ~$200–260M in dividends and bought back ~$440–450M of stock, and both trade at premium EV/EBITDA (enterprise value to earnings before interest, taxes, depreciation, and amortization) multiples versus most extractive industries — precisely because of local pricing power and long reserve lives. [8][9]
• Royalty/land and funds are niche and aggregates-tilted: FRP Holdings (FRPH) and Natural Resource Partners (NRP) for royalty exposure; XLB / PAVE / IFRA for diluted, diversified exposure. There is no pure-play stone ETF or streaming company. [14][24][28]
• Dimension stone (contrarian only): Caesarstone (CSTE) is an inverse/substitution bet, not a proxy — engineered quartz now faces its own silicosis backlash (Australia banned engineered-stone fabrication in 2024), which could push countertop share back toward natural stone. [6][15]

Private routes (the only way into dimension stone, and much of the crushed tail)

• Direct / PE ownership and regional roll-ups. The fragmented long tail — ~1,400 crushed-stone producers plus ~150 dimension-stone operators — earns the same local-monopoly cash flows the majors do, often at lower entry multiples. The standard playbook: buy an anchor quarry in a growth market, professionalize pricing and safety, add nearby reserves and distribution, integrate asphalt/ready-mix (crushed) or fabrication (dimension), and sell a regional platform to a strategic consolidator. Most operators fall under the SBA (Small Business Administration) size ceilings (500–850 employees by child code), making this a lower-middle-market and search-fund universe. [4][12][13]
• Mineral and royalty (land) ownership — leasing reserves to an operator for a per-ton or percentage royalty (typically with minimum annual rents; observed aggregate rates roughly $0.20–$5.00/ton by state), plus the 5–14% depletion shield — is the lowest-operational-risk exposure: inflation-linked, very-long-duration income without running the mine. But it is illiquid, appraisal-driven, dependent on compatible surface access, and has no securitized secondary market. [21][25]

The underwriting rule (both worlds)

The valuable asset is permitted, specification-grade rock inside an advantaged freight radius (crushed) or a permitted, architect-specified deposit with high intact-block recovery (dimension). Diligence the delivered-cost map and the site-level reserve life market by market — never the national average — and verify surface, mineral, access, and water rights independently.

Outlook

Base case (constructive, cyclically soft near-term). The structural story across ~96% of the group is intact: freight-protected local pricing, long reserve lives, permitting barriers that entrench incumbents, and tailwinds from infrastructure, reshoring, power, and data centers. USGS expects the price-supporting forces to persist into 2026 (Vulcan's own guide: volume +1–3%, price +4–6%), so revenue and margin dollars grind higher even in a flat-volume year. The realistic risks are cyclical (volume) and political (highway reauthorization) — not structural demand destruction. The dimension-stone ~4% is a mature, slowly consolidating, import-pressured niche where value holds on price/mix while tonnage drifts down, with tariff policy as its distinctive swing factor.

What to watch: the post-IIJA surface-transportation reauthorization; mortgage rates and housing; diesel prices; freight-adjusted price and cash gross profit per ton; site-specific (not national) reserve life; the M&A pipeline and deal multiples; the MSHA silica rule; and — for dimension stone only — tariff policy and the engineered-stone silicosis backlash.

Bottom line: 21231 is best read as one code, two businesses. The ~96% crushed-stone majority is a cyclical, real-asset infrastructure business with local-monopoly pricing — modest volume cyclicality, structural price escalation, fat per-ton margins, very long reserves, and near-zero transition risk — best owned through the large-cap aggregates equities or by holding permitted reserves in the path of growth. The ~4% dimension-stone minority is a small, private, provenance-and-freight specialty niche with no public access and a tariff-driven upside — owned only by PE, families, and mineral-rights holders. In neither case is this a "buy-the-commodity-price" bet; it is a buy-the-permitted-deposit-and-the-freight-moat bet. [2][5][6][8][9]

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Sources

1. U.S. Census Bureau — 2022 NAICS Manual: Industry 21231 (Stone Mining and Quarrying) and child codes 212311/212312/212313/212319; adjacent codes 212321, 213115, 327991, 327310/327410 (definitions, hierarchy, exclusions), 2022. https://www.census.gov/naics/
2. U.S. Census Bureau — 2022 Economic Census, NAICS 21231 (our ground truth): receipts $17.724B; 969 firms; CR4 32.0% / CR8 40.4% / CR20 52.4% / CR50 66.6%; HHI 340.7. https://data.census.gov/table/ECNSIZE2022.EC2200SIZECONCEN
3. U.S. Census Bureau — 2023 County Business Patterns, NAICS 21231 (our ground truth): 2,440 establishments; 43,124 employees; $3.408B annual payroll; $798.3M Q1 payroll. https://www.census.gov/programs-surveys/cbp.html
4. U.S. Census Bureau — 2022 Economic Census & 2023 County Business Patterns, child industries 212311/212312/212313/212319 (per-child receipts, firms, establishments, employment, payroll, concentration used to build the §2 contrast table). https://data.census.gov/
5. U.S. Geological Survey — Mineral Commodity Summaries 2026: Stone (Crushed) (2025 estimate ~1.5 Bt, ~$27B, ~$18.50/t; rock-type shares ~70% limestone / ~14% granite / ~15–16% other; ~72% construction end-use; net import reliance ~1%; reserves; IIJA), Feb 2026. https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-stone-crushed.pdf
6. U.S. Geological Survey — Mineral Commodity Summaries 2026: Stone (Dimension) (2025 estimate ~2.3 Mt, ~$460M, ~$200/t; ~81% net import reliance; ~150 companies; depletion allowance; reserves; tariffs), Feb 2026. https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-stone-dimension.pdf
7. U.S. Small Business Administration — Table of Small Business Size Standards (13 CFR §121.201): 212311 = 500, 212312 = 750, 212313 = 850, 212319 = 550 employees (2023). https://www.sba.gov/document/support-table-size-standards
8. Vulcan Materials Company (NYSE: VMC) — Form 10-K, FY2025 (226.8M tons; $21.98/t price; $10.65/t cash cost; $11.33/t cash gross profit; $8.66/t GAAP gross profit; 16.6B tons reserves; 63% owned / 37% leased; $128.6M royalties; capex; $259.8M dividends; $438.4M buybacks). https://www.sec.gov/Archives/edgar/data/1396009/000162828026009546/vmc-20251231.htm
9. Martin Marietta Materials (NYSE: MLM) — Form 10-K, FY2025 (198.5M tons; $23.30/t price; $8.45/t gross profit; ~16B tons reserves; ~85-yr life; energy sensitivity; ~$647M capital returns). https://www.sec.gov/Archives/edgar/data/916076/000119312526059193/mlm-20251231.htm
10. CRH plc (NYSE: CRH) — Form 10-K, FY2025 (736 U.S. pits/quarries; ~18.3B tons U.S. reserves). https://www.sec.gov/Archives/edgar/data/849395/000162828026009043/crh-20251231.htm
11. Amrize Ltd. (NYSE/SIX: AMRZ) — Form 10-K, FY2025 (376 N. American pits/quarries; 118.9M tons sold; June-2025 Holcim spin-off). https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=2035989&type=10-K
12. Summit Materials / Quikrete — Completion of merger, February 2025 (~$11.5B enterprise value; $52.50/share; Summit delisted). https://www.sec.gov/Archives/edgar/data/1621563/000095010325001807/dp224739_ex9901.htm
13. Private / family / foreign owners — Rogers Group; Luck Stone / Luck Companies; Blue Water Industries; Carmeuse; and, in dimension stone, Polycor (Birch Hill Equity Partners / Investissement Québec; Wynnchurch), Coldspring, Vermont Quarries (RED Graniti). Company disclosures and PR, 2016–2026. https://rogersgroupincint.com/; https://www.newswire.ca/news-releases/birch-hill-and-investissement-quebec-partner-with-polycor-management-to-acquire-world-leading-natural-stone-quarrier-844141499.html
14. FRP Holdings (Nasdaq: FRPH) — Form 10-K / 10-Q, FY2025 (aggregate mineral-royalty model; ~16,648 royalty acres; royalties on tons × price). https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=0000844059&type=10-K
15. Caesarstone Ltd. (Nasdaq: CSTE) — Form 20-F (engineered quartz as substitute for natural stone; ~90% crushed quartz + resin); Australia engineered-stone ban, 2024. https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=0001504379&type=20-F
16. U.S. Mine Safety and Health Administration — Lowering Miners' Exposure to Respirable Crystalline Silica, Final Rule, 89 FR 28218 (PEL 50 µg/m³; action level 25 µg/m³), Apr 2024. https://www.federalregister.gov/documents/2024/04/18/2024-06920/
17. U.S. MSHA / Federal Register — Silica rule; Delay of Effective Date (8th Circuit stay; indefinite metal/nonmetal delay), 2026. https://www.federalregister.gov/d/2026-06584
18. U.S. Bureau of Land Management — Saleable Minerals / Materials Act of 1947 (common-variety stone sold at fair market value; not locatable under the 1872 Mining Law). https://www.blm.gov/programs/energy-and-minerals/mining-and-materials/saleable-minerals
19. U.S. Environmental Protection Agency — Nonmetallic Mineral Processing NSPS (40 CFR Part 60 Subpart OOO); Mineral Mining & Processing Effluent Guidelines (40 CFR Part 436; dimension-stone subpart reserved); NPDES; CWA §404. https://www.epa.gov/eg/mineral-mining-and-processing-effluent-guidelines
20. Congressional Research Service / FHWA — Funding and Financing Highways under IIJA (~$350B federal highway funding, FY2022–2026; reauthorization overhang). https://www.congress.gov/crs-product/R47573
21. U.S. Code — 26 U.S.C. §613, Percentage Depletion (5% construction stone; 14% specialty; dimension-stone rates). https://uscode.house.gov/view.xhtml?req=(title:26%20section:613%20edition:prelim)
22. U.S. Bureau of Labor Statistics — Employer-Reported Workplace Injuries and Illnesses 2024; Fatal Occupational Injuries 2024 (TRC ~1.8–1.9 per 100; 3 fatalities NAICS 212312). https://www.bls.gov/iif/
23. Recent aggregates M&A — Martin Marietta/Blue Water ($2.05B, 2024); Martin Marietta/Quikrete asset exchange (2026); CRH/Arcosa (~$8.5B, pending 2026); Martin Marietta/Lhoist (~$13.5B, pending 2026). Company disclosures. https://ir.martinmarietta.com; https://www.crh.com
24. Natural Resource Partners L.P. (NYSE: NRP) — Form 10-K, FY2025 (mineral-rights partnership; aggregates a small share). https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=1171486&type=10-K
25. Rock Associates — Observed sand, gravel, and quarry royalty rates (~$0.20–$5.00/ton by state). https://www.rockassociates.com/post/sand-gravel-and-quarry-royalty-rates
26. U.S. Federal Trade Commission / Department of Justice — CRH/Ash Grove (Johnson County, KS local limestone market; 3-quarry divestiture); Vulcan/Aggregates USA (17-facility divestiture), 2017–2018 (local-market antitrust analysis). https://www.ftc.gov/; https://www.justice.gov/
27. National Funeral Directors Association — 2025 Cremation & Burial Report (~63% cremation; monument-demand headwind for dimension stone). https://www.nfda.org/news/statistics
28. State Street Global Advisors / Global X / iShares — Materials Select Sector SPDR (XLB); U.S. Infrastructure Development ETF (PAVE); U.S. Infrastructure ETF (IFRA) holdings, July 2026. https://www.ssga.com/us/en/individual/etfs/state-street-materials-select-sector-spdr-etf-xlb

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Data-quality notes

• Ground truth vs. reports. Group-level business figures — receipts, firms, concentration, HHI (2022 Economic Census); establishments, employment, payroll (2023 CBP) — are Histometrics' ingested federal statistics for NAICS 21231 [2][3]. Physical production, unit value, reserves, and trade are USGS by commodity [5][6]; company figures are 2025 SEC filings [8][9].
• The rollup reconciles on additive frames. The children's 2023 CBP establishments (2,440) and employees (43,124) sum exactly to the parent, and their 2022 receipts (~$17.72B) reconcile — because each establishment carries one primary code. Firm counts do not add (children list 1,043; parent 969) because a firm operating in multiple children is de-duplicated at the parent level [2][3][4].
• Frames are not interchangeable. USGS's ~$27B crushed-stone value exceeds the ~$17B of Census receipts for the crushed children because USGS counts crushed-stone quarries of every rock type (including quarries captive to plants classified elsewhere), in a different year, than the Census primary-code population [2][5].
• Not stated because unavailable. Our 21231 ground truth contains no group-level physical tonnage, reserve tonnage, unit value, per-ton cost/AISC-equivalent, or a single SBA size standard — those are undefined at this level; where used, physical/price data are USGS commodity series and per-child SBA standards, labeled as such. No numerical national reserve total exists for any of these codes; USGS characterizes reserves only qualitatively.
• Estimates and derivations. Per-child shares of the group are computed from [2][3][4]; USGS "(e)" values are USGS estimates; rock-type tonnages (~70%/14%/15–16%) are USGS shares of the crushed-stone total, not separately reported by NAICS.
• Market caps, tickers, yields, and multiples in §4 and §10 are approximate mid-2026 figures for context only, not drawn from the federal sources, and move with the market.