Sand, Gravel, Clay, and Ceramic & Refractory Minerals Mining — An Investor's Primer

U.S. industry group, NAICS 2022 code 21232. NAICS is the North American Industry Classification System, the government's standard code for an industry; this is a five-digit "industry" that rolls up three more detailed six-digit industries. This primer is for a general investing audience — both public-market investors (listed producers, their oilfield-service and building-materials parents, and sector funds) and private investors (private/private-equity-owned operators, and mineral- and royalty-rights owners). Business-economy figures come from our ingested federal statistics (U.S. Census Bureau); physical production and reserves come from the U.S. Geological Survey (USGS, the federal minerals-data agency) and, for the energy demand behind frac sand, the U.S. Energy Information Administration (EIA). Sources are labeled; the two measure different things and are shown side by side, not blended.

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1. Overview

NAICS 21232 is the "industrial rocks and dirt" corner of U.S. mining: the loose granular and clay materials that get dug from shallow surface pits, cleaned at the pit, and sold by the ton. It bundles three very different businesses under one code — the sand and gravel that goes into concrete and roads, the high-purity silica sand pumped into shale wells, and the clays behind brick, cat litter, and steel-furnace linings.

They share a family resemblance that shapes every investment in the group:

• They are commodity businesses, not scarcity stories. USGS says outright that resources of sand, gravel, and clay are "plentiful" to "extremely large" — the scarce asset is permitted, specification-quality material near the customer, not the rock itself. So "reserve life" is rarely the risk; permitting and freight geography are.
• Freight is the binding constraint. These products are heavy and cheap. Trucking a low-value ton even 30-50 miles can add 50-100% to its delivered price, which turns thousands of ordinary pits into local mini-monopolies. The lower a producer's delivered cost — mine cost plus freight — the more it wins, regardless of who has the best deposit.
• You cannot buy a pure play. There is no sand-and-gravel stock, no frac-sand exchange-traded fund (ETF, a basket security that trades like a share), and no clay royalty company. Public exposure comes bundled inside diversified building-materials, oilfield-service, or specialty-minerals firms; the majority of tonnage is owned privately, by private equity (PE), or by foreign parents.

But the three children diverge sharply on the things that actually drive returns — size, which commodity, price direction, who the customer is, how concentrated the market is, and whether the business is defensive or high-beta. That contrast is the whole point of this primer, and Section 2 leads with it.

One number to anchor the group. By our ground-truth federal count, the whole of NAICS 21232 was about $12.84 billion of business receipts, 2,617 establishments (individual pits/sites), 1,437 firms, and 36,740 employees in the most recent data [1][2]. That is a genuinely small slice of U.S. mining — smaller than the crushed-stone industry next door — and roughly two-thirds of it is a single child: construction sand and gravel.

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2. What's inside — the three children, and how they differ

The group splits into three six-digit industries. They look adjacent on an org chart and behave like different asset classes.

"Mt" = million metric tons. "CR4" = the combined revenue share of the four largest firms; "HHI" = Herfindahl-Hirschman Index, a 0-10,000 concentration score where below 1,500 is "unconcentrated." Physical mine value (USGS) exceeds Census receipts because USGS counts the whole commodity, including non-employer and captive pits the business census misses — see Section 3.

Read the table this way. Construction sand and gravel is the elephant — two-thirds of revenue but nearly nine-tenths of the sites, because it is a swarm of tiny local pits. Industrial sand is a fraction of the tonnage but sells for more than double the price per ton and is really an energy bet in mining clothing. Clay is the smallest and most boring — and that dullness is a feature, because its demand is spread across construction, consumer staples, and industry, so it does not boom or bust with any one market.

The single most useful distinction for an investor: all three are "price-takers" on paper, but they land in different places on a spectrum from local price-maker to global price-taker.

• Construction sand and gravel is effectively a local price-maker — freight is so punishing that each pit prices its own short-haul zone, and U.S. prices have compounded every year even as tonnage fell.
• Clay sits in the muted middle — negotiated, slow-moving contract prices by grade, with no exchange quote and only single-digit annual moves.
• Industrial (frac) sand is the closest to a true commodity price-taker — a homogeneous, substitutable product whose price swings hard with the shale cycle and periodic oversupply, occasionally below cost.

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3. How big it is

Two federal yardsticks measure two different things. Keep them separate — mixing them is the most common error in reading this group.

3.1 The business economy — U.S. Census Bureau (our ground-truth stats)

The Census counts employer businesses classified to NAICS 21232 and its children.

Implied average pay is about $80,500 per employee (our calculation: $2.96 billion ÷ 36,740) — well above the U.S. private-sector average, reflecting skilled, capital-intensive, often unionized mining and processing labor [2].

How the group splits (Census receipts and headcount). The three children add up cleanly:

(Receipts, establishments, and employees sum exactly to the group. Firm counts do not add up — 1,280 + 110 + 74 = 1,464 versus a group total of 1,437 — because a firm operating in more than one child is counted once at the group level; the small gap is de-duplication, not an error.)

Concentration at the group level is low. For all of NAICS 21232, the four largest firms hold just 15.5% of revenue (CR4), the top 8 hold 22.8%, the top 20 hold 36.4%, and the top 50 hold 51.9%, with an HHI of just 101.7 [1] — deep in "unconcentrated" territory. But that national figure is misleading about competition, for two different reasons that split by child:

• In construction sand and gravel, the true market is a 30-50 mile haul zone, where two or three permitted operators can behave as a local oligopoly — national fragmentation hides local pricing power.
• In industrial sand and clay, the national top tier is genuinely more concentrated (CR4 of 47% and 49%), but a long tail of tiny common-sand and common-clay pits dilutes the group index. The high-value niches within them — frac sand, kaolin, sodium bentonite — are more concentrated than any headline number shows.

3.2 Physical production and reserves — USGS

USGS canvasses the physical commodity, including small non-employer and captive pits the Census misses, so its universe is larger and its dollar value higher [4][5][6]:

Why the two sources differ — and the undercount. The Census $12.84 billion counts employer businesses' receipts; the USGS ~$18.9 billion values total physical output, including non-employer, captive, and cross-classified production (a pit owned inside an oilfield-service company or a paper maker shows up in USGS but not under a 21232 business). One firm can own many pits. These are not errors to reconcile — they answer different questions, and the Census figures materially undercount the full physical industry, most of all in construction sand and gravel. Treat USGS as the better gauge of the physical industry's economic size and Census as the size of the stand-alone business population; do not add or average them.

Reserves. USGS publishes no national reserve tonnage for any of the three — resources are "plentiful" to "extremely large." What is scarce is permitted, specification-grade material near demand. Company disclosures are more informative than any national figure: Vulcan holds ~16.6 billion tons of aggregate reserves; Smart Sand reports ~462 million tons of saleable silica; Minerals Technologies cites ~159 million tons of U.S. sodium-bentonite reserves (~100 years' life) [7][8][9]. The lesson repeats across all three: the constraint is permission, not geology.

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4. The investable universe

There is no pure play in any child. Public exposure comes through diversified producers and their parents; the majority of tonnage across the group is private, PE-owned, or foreign-owned. (Tickers, market caps, and financials appear only in this and the "how to invest" sections, per house style. Market-cap figures are approximate early-2026 order-of-magnitude values, not from the federal sources, and move daily — treat them as scale, not precision.)

212321 Construction sand & gravel — the majors. Sand and gravel rides inside a combined "aggregates" segment (crushed stone + sand and gravel), so a pure-212321 financial statement does not exist.

212322 Industrial (frac) sand — a thinned-out public field. A decade of boom, Chapter 11 filings, and take-privates left only a handful of listed names.

212323 Clay & ceramic/refractory minerals — one real public name.

Royalty and fund routes — a structural gap across all three. There is no aggregates, frac-sand, or clay royalty/streaming company comparable to the precious-metals royalty names, and no dedicated ETF for any child. The closest indirect routes: infrastructure ETFs (PAVE, IFRA) for aggregates, where materials are only ~13-22% of holdings; oilfield-services ETFs for frac sand; and, for asset-light sand-volume exposure, LandBridge (NYSE: LB), which books Permian surface royalties including frac sand [16]. Natural Resource Partners (NYSE: NRP) holds some aggregate royalties but is diversified across coal and other minerals [17]. Passive, securitized exposure to these commodities barely exists — this is a stock-selection and private-diligence group, not an index one.

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5. How the money works

The economics rhyme across the three children — freight-limited local pricing, abundant reserves, percentage-depletion tax shields, per-ton royalties — but the magnitude of commodity-price risk is what separates them.

Freight is the cost curve. For most mined commodities the cost curve is about ore grade; here it is about transportation. Because every product is heavy and cheap, the low-cost supplier is usually the one closest to the job, not the cheapest to dig. Vulcan moves ~80% of its aggregate tons directly from pit to customer by truck [7]; frac-sand logistics can be ~70% of delivered cost, which is why the supply base migrated into the Permian basin [18]; and low-value common clay (~$21/ton) can't travel more than a few tens of miles before freight prices it out. Owning the logistics — conveyors, rail terminals, wet-sand handling — is where differentiated returns live, especially in frac sand.

No standardized cost metric — use the price-cost spread per ton. Metals miners quote all-in sustaining cost (AISC) per ounce; oil producers quote lifting and finding-and-development (F&D) cost per barrel. This group has no standardized equivalent, because operators treat freight, depletion, and internal transfers differently and most are private or a small segment of a diversified parent. The useful gauge is the freight-adjusted price-cost spread per ton. Vulcan's 2025 aggregates: ~$21.98 selling price, ~$10.65 cash cost, ~$11.33 cash gross profit per ton [7]. Smart Sand's 2025 frac sand: roughly $60 revenue against ~$53 cost, a thin ~$7/ton spread that shows how completely freight, price, and utilization dominate a heavy-cheap product [8]. In clay, the best margin proxy is Minerals Technologies' specialty-segment operating margins of ~11-17% — healthy precisely because the money is in processing and formulation, not digging [9].

Where the children diverge on price risk.

• Construction sand & gravel — a local price-maker. Prices compounded through the cycle even as volumes fell; the earnings engine is the widening spread, not a spot quote. Capital returns are a steady, growing dividend/buyback pattern — a "quality cyclical," not a boom-bust payer.
• Industrial sand — a double commodity bet. Oil and gas prices set completion budgets (demand), and sand supply/demand sets the realized price. Mostly fixed costs plus a swinging price equals high operating leverage — exceptional cash in an up-cycle, insolvency at the trough. Expect boom-bust distributions.
• Clay — muted and negotiated. No exchange price; USGS unit values moved only single digits over five years. This behaves like a defensive industrial-minerals business with below-average commodity beta and a steady, less price-linked payout.

Reserves, depletion, and royalties (common to all three). Reserves are added by acquisition, not exploration — the scarce input is permission. As pits deplete, the U.S. tax code grants a percentage-depletion allowance — a modest permanent tax shield of 5% for construction sand and gravel and common clay, and 14% for higher-value industrial sand and premium clays (kaolin, bentonite, ball/fire clay, fuller's earth) [19]. Landowners who lease pit rights collect a per-ton or percentage royalty — commonly ~$0.50-$1.70/ton in sand, or ~5-15% of sales — the analog of an oil-and-gas mineral-royalty interest: a claim on gross tonnage with no operating cost, but still bearing volume, permit, title, and operator-credit risk. A crucial diligence point across the group: whether a deed's general "mineral" reservation even conveys common sand, gravel, or clay — under some state law it does not.

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6. Demand drivers

The group's demand is the sum of three unrelated end-market bets, which is why the children rarely peak or trough together.

• 212321 Construction sand & gravel → U.S. construction. 2025 end-use: concrete aggregate ~42%, road base ~20%, fill ~12%, asphalt ~9% [4]. The most durable leg is public infrastructure: the 2021 Infrastructure Investment and Jobs Act (IIJA) provided ~$350 billion for federal highways across fiscal years 2022-2026, and its highway authorization expires after FY2026 — the single biggest demand-swing variable into 2027 [20]. Residential construction (rate-sensitive) is the main recent drag; data centers, reshoring, and energy projects are new supports.
• 212322 Industrial sand → shale completions. Frac sand is ~81% of tonnage [5], so demand ≈ completed wells × lateral length × proppant per foot. Rig count alone misleads: sand per well keeps rising as laterals lengthen, which held tonnage near records even in a soft rig environment. EIA (the U.S. Energy Information Administration) sees U.S. crude and LNG (liquefied natural gas) exports rising through 2027, supporting completion volumes — though not necessarily prices if sand capacity stays ample [21].
• 212323 Clay → everything at once. Brick/cement (construction), ceramic tile, pet litter (the largest single bentonite use, ~48%, and structurally growing), drilling mud (~22% of bentonite, cyclical with rigs), paper (in secular decline), paint/plastic fillers, and refractories. This diversification is the source of clay's defensiveness — no single market can sink it. Notably, none of the three is a critical-minerals or electric-vehicle story; the thesis is construction, energy, and consumer staples, not a green-transition supercycle.

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7. Regulation

Regulation is broadly common across the group, because all three are shallow, private-land, state- and locally permitted surface mining. The federal leasing regime that dominates hardrock metals and oil-and-gas matters far less here.

• Mine safety — MSHA (federal). Every pit and mill is regulated by the Mine Safety and Health Administration (MSHA) under the Mine Act: inspections, miner training, citation authority. The shared active item is MSHA's April 2024 rule tightening the respirable crystalline-silica exposure limit to 50 micrograms per cubic meter — most acute for industrial (quartz) sand, real for the other two. (For metal/nonmetal mines the conforming compliance deadlines are, as of mid-2026, delayed under a judicial stay; the hazard and prospective cost remain, but the new limits are not yet fully enforceable [22].)
• Federal land — BLM (minor). Common-variety sand, gravel, and clay are "saleable" mineral materials sold at fair market value by the Bureau of Land Management (BLM) under the Materials Act, not stakeable 1872-law claims. Because the group sits mostly on private and state land, BLM is a small factor for all three.
• Environment — EPA and states. Clean Water Act (CWA) Section 404 governs dredge-and-fill in wetlands and waterways; NPDES stormwater permits (the National Pollutant Discharge Elimination System, the federal water-discharge program) and EPA effluent and dust standards apply; reclamation and bonding are largely state-administered [23].
• Local zoning — the binding constraint. Because deposits are only valuable near demand, local zoning and conditional-use permitting — not resource availability — decide whether a pit can open. NIMBY opposition and multi-year entitlements are the group's chief chokepoint, pushing new pits farther from cities and tightening urban supply.
• Taxes. No dominant federal production royalty on private-land output; some states levy severance taxes (e.g., Wyoming's 2% on bentonite; Texas began taxing frac sand as a processed material on July 1, 2025). The 5%/14% federal percentage-depletion allowance is the shared tax feature.

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8. Consolidation

The structural pattern is the same across all three: a concentrated top rolling up a fragmented tail, with the majors growing by buying permitted reserves because greenfield permitting near demand is so hard.

• Construction sand & gravel — the deepest roll-up pipeline (~85% of pits are sub-20-employee independents). Landmark deals: Quikrete's ~$11.5B take-private of Summit Materials (2025); Holcim's spin-off of Amrize (2025); and, announced June 2026, CRH's ~$8.5B acquisition of Arcosa and Martin Marietta's ~$13.5B combination with Lhoist North America [11][24]. Barriers to entry are high and rising — a genuine moat.
• Industrial sand — consolidation came through distress and integration: Chapter 11 filings (Hi-Crush, Covia), Apollo's take-private of U.S. Silica, Atlas's roll-up of Hi-Crush, ProFrac's integration of Alpine Silica [13][14]. The market fragments in booms and consolidates in busts.
• Clay — a classic mature-market roll-up: KaMin bought BASF's global kaolin business (2022); Wyo-Ben bought M-I SWACO's bentonite plants (2023); and, pending as of early 2026, Burgess Pigment agreed to acquire Thiele Kaolin [25]. The logic everywhere: consolidate reserves, lift plant utilization, broaden the grade portfolio, and gain freight and contract leverage.

Antitrust review focuses on local overlap (divestitures are common) precisely because the relevant market is a haul zone, not the nation.

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9. Risks

Lead risk — commodity-price and volume cyclicality, but of three different flavors. This is the group's defining exposure, and getting the flavor right is the whole underwriting task:

• Construction sand & gravel: volume swings with construction while local price stays sticky-to-rising; operating leverage magnifies the earnings hit in a downturn even when price holds. Cyclical, not defensive.
• Industrial sand: the sharpest risk in the group — price is hostage to shale completions and periodic oversupply, and high fixed costs turn modest price moves into large earnings swings and, at the trough, insolvency (the Hi-Crush/Covia bankruptcies are the cautionary tale).
• Clay: the mildest — a recession hits tonnage more than price, and pet litter and purification provide defensive ballast the others lack.

Shared secondary risks:

• Cost inflation — diesel/freight is the dominant variable cost across all three; a fuel spike can strand freight-disadvantaged reserves and compress margins faster than slow contract prices pass it through.
• Permitting and zoning — the defining threat to supply growth everywhere; multi-year entitlements and NIMBY opposition can block new pits and sterilize owned reserves.
• M&A overpayment / valuation — scarce permitted assets can be excellent businesses but poor investments at prices that assume perpetual pricing power; the aggregates majors trade at premium "quality cyclical" multiples that embed continued price gains — a de-rating risk if volumes or infrastructure funding disappoint.
• Public-funding cliff — the IIJA highway authorization expires after FY2026 (aggregates-specific but material to the whole group's largest child).
• Demand concentration — frac sand's ~81% tie to shale completions is a genuine energy-transition/stranded-asset risk if U.S. drilling declines durably; clay's paper-grade kaolin faces secular decline.
• Environment, safety, weather — CWA §404, silica dust, reclamation obligations, and weather-driven quarterly noise.

What is not a major risk for most of the group: energy-transition/stranded-asset risk is minimal for construction aggregates and clay — roads, foundations, brick, and cat litter are needed under essentially every decarbonization scenario, and aggregates arguably benefits from transition capex (grid, data centers, EV plants). The exception is industrial sand, whose fossil-fuel demand concentration is a real, coal-like (if less acute) overhang.

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10. How to invest, and outlook

Public routes

• Aggregates (212321) — the primary vehicle. Vulcan (VMC) and Martin Marietta (MLM) are the closest thing to pure-play aggregates compounders — large-cap, investment-grade, local-pricing-power reserve annuities with steadily growing dividends and buybacks. CRH, Amrize, Knife River, Eagle Materials, CEMEX, and Heidelberg add diversified building-materials exposure. Trade as premium "quality cyclicals," so multiples can compress if volumes or infrastructure funding disappoint [7][10][11].
• Frac sand (212322) — cyclical energy-beta. Atlas Energy Solutions (AESI) is the cleanest listed play (low-cost Permian tons + owned logistics), with Smart Sand (SND) and ProFrac (ACDC) as smaller/hybrid names. Expect a boom-bust dividend/buyback pattern; judge distributions against through-cycle free cash flow, not peak earnings [8][12][13].
• Clay (212323) — a defensive single-name. Minerals Technologies (MTX) is the one direct listed play — a specialty-minerals story with a consumer-staples (cat litter) growth kicker, below-average commodity beta, and a steady payout (watch its talc-litigation liabilities); Oil-Dri (ODC) is a more litter-levered micro-cap [9][15].
• Funds/royalties. No pure ETF or royalty stock exists for any child; the closest indirect routes are infrastructure ETFs (PAVE, IFRA) and oilfield-services ETFs, both of which dilute the exposure [16][17].

Private routes

• Operating roll-ups. The fragmented long tail — deepest in construction sand and gravel — is a fertile buy-and-build arena. Underwrite pit by pit: permitted reserve quality, remaining permit life, haul distance, local competition, and reclamation liabilities, because consolidated earnings can hide a poor reserve or an expiring permit.
• Low-cost reserves + logistics (frac sand). The durable edge is low-cost in-basin reserves paired with owned conveyors/terminals; the classic error is underwriting a "normalized" sand price that assumes competitors stay disciplined.
• Reserve-control + processing (clay). Value creation is operational — buy a regional producer, add bolt-ons, invest in beneficiation and technical service, migrate mix toward higher-value grades.
• Mineral and royalty interests (all three). Owning the reserve-bearing land and leasing pit rights yields a capital-light, operating-cost-free per-ton or percentage royalty — lower risk and lower upside than operating, illiquid, and bespoke (there is no securitized market). Key diligence is title (does the deed convey the sand/gravel/clay?), reserve life, permitting status, and operator credit.

Outlook

• Near term is a study in contrast. Construction sand and gravel: volumes soft-to-flat but price still rising (~$14.50/ton), the signature resilient pattern [4]. Frac sand: soft on price, resilient on volume — value pressed toward ~$36/ton by oversupply even as rising proppant intensity keeps tonnage near records [5][21]. Clay: flat volume, gently rising sticky prices — more of the same low-single-digit, GDP-linked grind [6].
• The pivotal variables: for the group's largest child, the post-IIJA federal-funding path after FY2026 and a rate-driven housing recovery; for frac sand, the shale completion cycle; for clay, continued pet-litter/purification growth offsetting paper decline. Consolidation continues in all three.
• Structural tailwind for two of three: aggregate- and clay-intensive megaprojects (data centers, reshoring, grid) partly offset residential softness and carry minimal transition risk; frac sand is the one child whose long-run demand is genuinely tied to the fate of U.S. drilling.

Bottom line. NAICS 21232 is three commodity-mining businesses that share a freight-driven local moat and abundant reserves but diverge on everything that sets returns. Construction sand and gravel (two-thirds of the group) is a mature, pricing-resilient "quality cyclical" with a genuine local moat and minimal transition risk. Industrial sand is a high-beta, boom-bust proxy for U.S. shale completions where value accrues to the cheapest permitted ton delivered to the wellsite. Clay is a defensive, consolidation-driven specialty-minerals corner where the money is made downstream of the shovel. Across all three, the scarcity that matters is permits, grade, and freight geography — not the rock — and the durable ways to make money are low-cost permitted reserves near demand, owned logistics, and passive per-ton royalties.

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Sources

1. U.S. Census Bureau, 2022 Economic Census — Summary Statistics & Concentration, NAICS 21232 and children 212321/212322/212323 (receipts, firms, CR4/CR8/CR20/CR50, HHI; our ingested ground-truth statistics). https://data.census.gov/table/ECNBASIC2022.EC2200BASIC
2. U.S. Census Bureau, County Business Patterns 2023 — NAICS 21232 and children (establishments, employment, payroll; our ingested ground-truth statistics). https://www.census.gov/programs-surveys/cbp.html
3. U.S. Census Bureau, 2022 NAICS Manual — definitions of 212321 (Construction Sand and Gravel), 212322 (Industrial Sand), 212323 (Kaolin, Clay, and Ceramic and Refractory Minerals Mining). https://www.census.gov/naics/?year=2022
4. U.S. Geological Survey, Mineral Commodity Summaries 2026 — Sand and Gravel (Construction), February 2026. https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-sand-gravel.pdf
5. U.S. Geological Survey, Mineral Commodity Summaries 2026 — Sand and Gravel (Industrial), February 2026. https://pubs.usgs.gov/periodicals/mcs2026/mcs2026.pdf
6. U.S. Geological Survey, Mineral Commodity Summaries 2026 — Clays (and Feldspar, 2025), February 2026. https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-clays.pdf
7. Vulcan Materials Company, 2025 Form 10-K, U.S. SEC EDGAR. https://www.sec.gov/Archives/edgar/data/1396009/000162828026009546/vmc-20251231.htm
8. Smart Sand, Inc., 2025 Form 10-K, U.S. SEC EDGAR. https://www.sec.gov/Archives/edgar/data/1529628/000152962826000006/snd-20251231.htm
9. Minerals Technologies Inc., 2025 Form 10-K, U.S. SEC EDGAR. https://www.sec.gov/Archives/edgar/data/891014/000089101426000067/form10k.htm
10. Martin Marietta Materials, 2025 Form 10-K, U.S. SEC EDGAR. https://www.sec.gov/Archives/edgar/data/916076/000119312526059193/mlm-20251231.htm
11. CRH plc, 2025 Form 10-K; CRH, CRH to Acquire Arcosa for $8.5 Billion, June 2026. https://www.sec.gov/Archives/edgar/data/849395/000162828026009043/crh-20251231.htm
12. Atlas Energy Solutions Inc., 2025 Form 10-K, U.S. SEC EDGAR. https://www.sec.gov/Archives/edgar/data/1984060/000119312526067145/aesi-20251231.htm
13. ProFrac Holding Corp., 2025 Form 10-K, U.S. SEC EDGAR. https://www.sec.gov/Archives/edgar/data/1881487/000119312526106120/acdc-20251231.htm
14. U.S. Silica / Apollo, U.S. Silica Completes Transaction with Apollo Funds (~$1.85B), July 2024. https://www.prnewswire.com/news-releases/us-silica-completes-transaction-with-apollo-funds-302211472.html
15. Oil-Dri Corporation of America, Fiscal 2025 Form 10-K, U.S. SEC EDGAR. https://www.sec.gov/Archives/edgar/data/74046/000162828025044686/odc-20250731.htm
16. Global X, U.S. Infrastructure Development ETF (PAVE); iShares, U.S. Infrastructure ETF (IFRA); LandBridge Company (NYSE: LB). https://www.globalxetfs.com/funds/pave
17. Natural Resource Partners L.P., 2025 Form 10-K (diversified mineral royalties). https://www.sec.gov/Archives/edgar/data/1171486/000143774926006147/nrp20251231_10k.htm
18. American Oil & Gas Reporter / Permian Basin Oil and Gas Magazine — in-basin vs. Northern White frac-sand logistics economics (secondary/trade press). https://www.aogr.com/magazine/frac-facts/permian-driving-frac-sand-supply-shift
19. Office of the Law Revision Counsel, 26 U.S.C. §613 — Percentage Depletion (5% sand/gravel/common clay; 14% industrial sand and premium clays). https://uscode.house.gov/view.xhtml?req=(title:26+section:613+edition:prelim)
20. Federal Highway Administration, Infrastructure Investment and Jobs Act (IIJA) Funding, updated 2026. https://highways.dot.gov/iija/funding
21. U.S. Energy Information Administration, Short-Term Energy Outlook, July 2026 (crude and LNG-export outlook). https://www.eia.gov/outlooks/steo/report/index.php
22. U.S. Department of Labor / MSHA, Final Rule Reducing Miners' Exposure to Respirable Crystalline Silica (April 2024) and Delay of Effective Date for Metal/Nonmetal (judicial stay, 2026). https://www.msha.gov/regulations/rulemaking/silica
23. U.S. Environmental Protection Agency, Permit Program under Clean Water Act Section 404; Mineral Mining and Processing Effluent Guidelines. https://www.epa.gov/cwa-404/permit-program-under-cwa-section-404
24. Summit Materials / QUIKRETE merger (~$11.5B, 2025); Holcim spin-off of Amrize (2025); Martin Marietta / Lhoist North America (~$13.5B, June 2026). https://ir.martinmarietta.com/news-releases
25. KaMin / BASF kaolin acquisition (2022); Wyo-Ben / M-I SWACO (2023); Burgess Pigment agreement to acquire Thiele Kaolin (pending, March 2026). https://www.thielekaolin.com/index.php/news/burgess-pigment-co-acquire-thiele-kaolin-company