Barite (barium sulfate, BaSO4, CAS 7727-43-7) is the primary weighting agent of drilling fluids, and more than 90 % of the barite sold in the United States goes into oil and gas drilling fluids (USGS Mineral Commodity Summaries 2026). Any drilling fluid heavier than its base liquid needs a fine, dense solid, and barite is the reference one.
API Spec 13A defines two density grades, Barite 4.2 g/mL and Barite 4.1 g/mL. Raising 10.0 lb/gal (1.20 sg) mud to 12.0 lb/gal (1.44 sg) takes about 128 lb of Barite 4.2 g/mL per bbl of starting mud (365 kg/m3), and the lower grade needs about 1.3 % more.
Four API Spec 13A requirements define barite quality; offshore, the United States caps mercury and cadmium in stock barite and OSPAR lists barite on PLONOR; and the United States imports more than 75 % of the barite it uses (USGS MCS 2026).
Standards and regulations are checked against their issuing bodies, product values against the named data sheet and figures against the dated source named in the sentence; see our methodology and fact-checking.
The identity block below lists the names, registry numbers and constants of drilling-grade barite.
| Attribute | Value |
|---|---|
| Canonical name | Barite (drilling-grade barium sulfate) |
| Synonyms | baryte, barytes, barium sulfate, heavy spar, API barite, drilling-grade barite, stock barite |
| CAS number | 7727-43-7 (barium sulfate); also 13462-86-7 (mineral barite) |
| EC number | 231-784-4 (barium sulfate); also 236-664-5 (mineral barite) |
| Formula | BaSO4 |
| Molecular weight | 233.39 g/mol |
| Substance type | mineral / natural substance |
| Chemical class | inorganic sulfate mineral (alkaline earth metal sulfate) |
| Specific gravity, pure BaSO4 | 4.50 |
| Mohs hardness | 3 to 3.5 |
| API Spec 13A grades | Barite 4.2 g/mL and Barite 4.1 g/mL |
| Hazard line | No harmonised classification captured; see supplier SDS |
What Is Drilling-Grade Barite?#
Drilling-grade barite is ground barium sulfate that meets API Spec 13A clause 7 as Barite 4.2 g/mL (density 4.20 g/mL minimum) or Barite 4.1 g/mL (4.10 g/mL minimum), while pure barium sulfate has a specific gravity of 4.50.
Barite has a Mohs hardness of 3 to 3.5 and is sold as a gray, pink or tan powder whose color depends on its impurities. Over 85 % of world barite goes into drilling fluids (AADE-24-FTCE-102, citing Bleiwas and Miller 2015). The class page compares barite and other weighting agents by density and solubility.
Is barite the same as barium sulfate?#
Yes: barite is the natural mineral form of barium sulfate, and ECHA holds two entries, barium sulfate (CAS 7727-43-7, EC 231-784-4) and mineral barite (CAS 13462-86-7, EC 236-664-5). US offshore rules add a third name, stock barite, which 40 CFR 435.11(ii) defines as the barite used to formulate a drilling fluid. Barium sulfate scale in production systems is a separate field.
Why Is Barite Used in Drilling Mud?#
Barite is used in drilling mud because it raises mud weight with an inert, high-density solid, so the mud column exerts enough hydrostatic pressure to control formation pressure and support the wellbore. Dissolved salts such as calcium bromide raise brine density but are not weighting materials, which are finely divided solids of high specific gravity.
Three uses rest on that density: weighted muds, including HPHT and deepwater muds; kill-weight fluid and weighted pills; and barite plugs.
How does barite work as a weighting agent?#
Barite adds density in proportion to its volume fraction: each particle replaces base fluid with a solid of 4.1 sg or more, with no chemical reaction except through accessory minerals. Barite adds density, not viscosity; the gel structure that holds it in suspension comes from clays or polymers.
In a weight-up, final mass equals starting mud mass plus barite mass, and final volume equals starting volume plus barite volume. The doses here use 35 lb/gal (4.2 sg) barite. A mud balance reads the resulting gain in drilling fluid density in lb/gal or sg.
Barite by fluid system#
Barite weights all water-based and non-aqueous muds, such as KCl-polymer, diesel oil-based and synthetic-based systems; the exception is potassium formate brine.
The table below compares barite by fluid system.
| Fluid system | Barite role | Basis or note |
|---|---|---|
| water-based mud | density by weight-up | all water-based muds |
| oil-based mud | 377 lb/bbl (1,076 kg/m3) | 15 lb/gal (1.80 sg) diesel oil-based example formulation (Scientific Reports, 2024) |
| synthetic-based mud | weighted like oil-based mud | stock barite limits apply when cuttings are discharged on the US OCS |
| Potassium formate, one of the formate brines | not used | barite dissolves |
The oil-based formulation is a published example (Scientific Reports, 2024), not a field range.
What Do the API Barite Grades Require?#
API Spec 13A sets four requirements for barite: density, water-soluble alkaline earth metals as calcium, residue above 75 µm and particles below 6 µm (19th edition, Table 2 as replaced by Addendum 2, 2022).
The table below compares both grades with test precision.
| Requirement | Barite 4.2 g/mL | Barite 4.1 g/mL | Repeatability / reproducibility |
|---|---|---|---|
| Density, g/mL | 4.20 min | 4.10 min | 0.022 / 0.030 g/mL |
| Water-soluble alkaline earth metals as calcium, mg/kg | 250 max | 250 max | 9.2 / 23.0 mg/kg |
| Residue above 75 µm, % by mass | 3.0 max | 3.0 max | 0.22 / 0.50 % |
| Particles below 6 µm equivalent spherical diameter, % by mass | 30 max | 30 max | 1.7 / 2.5 % |
API Spec 13A, 19th edition, Table 2 and precision Table B.1 as replaced by Addendum 2 (2022).
The governing text is API Spec 13A, 19th edition (2019) with Addendum 1 (2020), Addendum 2 (2022) and Errata 1 (2024), the current edition (API Standards Plan, checked 2026-10-27); a 20th edition is in development. API Spec 13A is a specification for manufacturers covering 13 materials; its ISO counterpart is ISO 13500:2008 with Cor 1:2009 and Amd 1:2010. It sets no mercury or cadmium limit.
Barite 4.2 g/mL and Barite 4.1 g/mL#
Barite 4.2 g/mL and Barite 4.1 g/mL differ only in minimum density; API issued Barite 4.1 g/mL in 2010 in response to dwindling reserves of 4.2-SG barite (USGS MCS 2026).
API cautions that Barite 4.1 g/mL "may not be appropriate for higher mud weights". On the dose table below, the lower grade needs about 1.3 % more barite by mass from 10.0 to 12.0 lb/gal (1.20 to 1.44 sg) and about 2.5 % more from 16.0 to 18.0 lb/gal (1.92 to 2.16 sg).
Is 4.1 g/mL barite off-spec?#
No: Barite 4.1 g/mL is a full API Spec 13A grade with the same calcium, residue and fine-particle limits as Barite 4.2 g/mL. Its packages carry the label "Barite 4.1 g/mL" or a trade name.
Micronized barite and other non-API grinds#
Micronized barite is a sub-API grind, not an API grade, so a quote for it names the particle size and the product data sheet instead of an API grade.
Barite Dose per Weight-Up#
Raising 10.0 lb/gal (1.20 sg) mud to 12.0 lb/gal (1.44 sg) takes about 128 lb of Barite 4.2 g/mL per bbl of starting mud (365 kg/m3). Each further 2 lb/gal step needs more barite, because the dose rises as the target approaches the barite density.
Each dose follows from a mass balance on the starting volume, and a mud weight calculator applies the same balance to other start and target weights.
Barite dose by target density#
Barite dose rises with target density because the margin to the barite density shrinks: 12.0 to 14.0 lb/gal needs 140.0 lb/bbl (399.4 kg/m3), but 16.0 to 18.0 lb/gal needs 172.9 lb/bbl (493.4 kg/m3). The doses apply to water-based and non-aqueous muds alike, because they rest on density, not chemistry.
The table below compares calculated doses for both grades.
| From lb/gal (sg) | To lb/gal (sg) | Barite 4.2 g/mL, lb/bbl (kg/m3) | Barite 4.1 g/mL, lb/bbl (kg/m3) | Volume increase, bbl per 100 bbl (4.2 grade) |
|---|---|---|---|---|
| 10.0 (1.20) | 12.0 (1.44) | 127.8 (364.7) | 129.4 (369.1) | 8.70 |
| 10.0 (1.20) | 13.0 (1.56) | 200.5 (571.9) | 203.2 (579.8) | 13.64 |
| 12.0 (1.44) | 14.0 (1.68) | 140.0 (399.4) | 142.2 (405.6) | 9.52 |
| 14.0 (1.68) | 16.0 (1.92) | 154.7 (441.5) | 157.8 (450.2) | 10.53 |
| 16.0 (1.92) | 18.0 (2.16) | 172.9 (493.4) | 177.2 (505.7) | 11.76 |
Calculated doses per bbl of starting mud, not field values.
Highest densities reached with barite#
No single maximum density applies to every barite mud: the reachable weight depends on the formulation, and each 2 lb/gal step in the table above needs more barite than the step before it.
What Limits Barite in a Drilling Fluid?#
Barite has no temperature limit as a mineral; its limits in a drilling fluid come from settling (sag), which rises with temperature and hole inclination, and from potassium formate brines, in which it dissolves.
Barite stays suspended only while the gel structure carries it, and deviated and hot wells raise the risk of barite sag, the settling of barite out of a static or flowing mud.
Barite in formate brines#
Barite dissolves in potassium formate brine, more as temperature rises, forming barium formate, so formate drill-in fluids use manganese tetroxide instead (AADE-14-FTCE-44). Manganese tetroxide has a specific gravity of about 4.8 and dissolves in acid.
Which Barite Impurities React with the Mud?#
Barite reacts with the mud only through four accessory minerals, never through barium sulfate itself (API Spec 13A, 18th edition (2010) text).
The four accessory minerals and the ion each releases are listed below.
- Gypsum: calcium
- Siderite: carbonate at high pH
- Dolomite: carbonate at high pH
- Pyrrhotite: sulfide at high temperature and pH
API RP 13K (4th edition, 2022), Chemical Analysis of Barite, covers the laboratory analysis of these impurities, and the 250 mg/kg calcium limit is the API screen for soluble calcium. The ions they release are a form of drilling fluid contamination in the mud.
Quartz, low-grade barite and solids analysis#
Quartz is the most common contaminant of low-grade barite (AADE-24-FTCE-102).
The table below compares low-gravity solids carried by barite grade.
| Barite SG | Low-gravity solids carried, vol % relative to pure 4.5 SG barite |
|---|---|
| 4.2 | 15.8 |
| 4.1 | 21.1 |
| 4.0 | 26.3 |
| 3.9 | 31.6 |
Contaminants liberated below 75 µm behave as low-gravity solids in the mud, and a solids calculation that assumes the low-grade barite's SG under-reports low-gravity solids.
Which Tests Verify Barite Quality?#
Four API Spec 13A tests verify barite (density by Le Chatelier flask, water-soluble alkaline earth metals as calcium, residue above 75 µm and particles below 6 µm), and API RP 13K (4th edition, 2022) covers its chemical analysis. The density test fills the flask with kerosene or mineral spirits in a bath at 90 degF (32 +/- 0.5 degC), 18th edition (2010) text.
The table below compares barite and mud tests.
| Test | What it measures | Method and edition |
|---|---|---|
| Density (API Spec 13A tests) | g/mL of the barite | Le Chatelier flask, API Spec 13A |
| Water-soluble alkaline earth metals as calcium | mg/kg soluble calcium | API Spec 13A |
| Residue above 75 µm | % by mass of coarse particles | API Spec 13A |
| Particles below 6 µm | % by mass of fines | API Spec 13A |
| Chemical analysis | impurities such as gypsum, siderite and pyrrhotite | API RP 13K, 4th edition, 2022 |
| Mud density after weight-up (mud balance test) | lb/gal (sg) of the mud | API RP 13B-1, 6th edition, 2026; API RP 13B-2, 6th edition, 2023 |
| Solids content (mud retort analysis) | vol % solids and liquids | API RP 13B-1, 6th edition, 2026; API RP 13B-2, 6th edition, 2023 |
After weight-up, field tests check the mud, not the barite.
Test precision and acceptance disputes#
Interlaboratory reproducibility of barite density is 0.030 g/mL, so a lot reading within 0.030 g/mL of the 4.20 g/mL limit is within test precision. API's calibration barite, lot 005, reads 4.22 g/mL with an acceptable range of 4.19 to 4.25 g/mL, and conformity rests on a composite sample of no more than one day's production.
Is Barite Hazardous? Safety and Exposure Limits#
Barite carries no harmonised EU CLP classification; its hazard line reads "No harmonised classification captured; see supplier SDS". US exposure limits for barium sulfate dust are a NIOSH REL of 10 mg/m3 total and 5 mg/m3 respirable and an OSHA PEL of 15 mg/m3 total and 5 mg/m3 respirable (TWA).
Barium sulfate (EC 231-784-4) is REACH registered, the mineral entry (EC 236-664-5) shows no registration, and barite is not on the Candidate List (ECHA CHEM, checked 2026-10-26). Barium sulfate is active on the TSCA Inventory as Sulfuric acid, barium salt (1:1), with reports in the 2020 and 2024 Chemical Data Reporting (EPA Substance Registry Services, checked 2026-10-27). Barite is on the final 2025 US List of Critical Minerals (Federal Register, 2025-11-07).
What Offshore Discharge Rules Apply to Barite?#
Offshore discharge rules treat barite in three ways: US limits on mercury and cadmium in stock barite, an OCNS group instead of a CHARM band in the UK and the Netherlands, and a PLONOR listing under OSPAR.
The table below compares offshore status by jurisdiction.
| Jurisdiction | Instrument | What applies to barite |
|---|---|---|
| US OCS and Cook Inlet | US offshore discharge rules (40 CFR 435): sections 435.13 (BAT), 435.15 (NSPS), 435.43 (Cook Inlet) | Hg 1 mg/kg and Cd 3 mg/kg dry weight maximum in stock barite |
| UK and Netherlands | Offshore Chemical Notification Scheme (OCNS), run by Cefas | OCNS group A to E on PBT data, no CHARM band, product-specific |
| North-East Atlantic | OSPAR PLONOR list (OSPAR Agreement 2013-06, Update 2026) | listed as barite and as barium sulfate |
Mercury and cadmium limits for US stock barite#
40 CFR 435.13 (BAT) and 435.15 (NSPS) cap mercury at 1 mg/kg and cadmium at 3 mg/kg dry weight in any single sample of stock barite, the barite used to formulate the fluid (40 CFR 435.11(ii)).
The limits apply to water-based mud discharged beyond 3 mi (4.8 km) from shore and to stock barite in non-aqueous mud whose cuttings are discharged, and the same limits apply in Cook Inlet (40 CFR 435.43). Discharged water-based mud must also pass a 96-hour LC50 of at least 3 % by volume of the suspended particulate phase. The section 435.13 text dates from 77 FR 29836 (2012-05-18), and part 435 was last amended on 2021-01-04.
Barite under the UK and Dutch notification scheme#
The Offshore Chemical Notification Scheme gives inorganic products such as barite an OCNS group from A (most hazardous) to E on PBT data rather than a CHARM hazard-quotient band, and the group of a product is product-specific. Barite and barium sulfate are on the PLONOR list (OSPAR Agreement 2013-06, Update 2026). OSPAR notes that barite contains traces of heavy metals such as lead.
Barite Suppliers, Grades, Packaging and Origin#
A barite quote is specified by its API grade plus four further items, and the supply behind it rests largely on imports. US net import reliance for barite exceeds 75 % of apparent consumption (USGS MCS 2026), and domestic barite comes from three companies mining at four operations in Nevada.
The five items of a barite specification are listed below.
- Grade: Barite 4.2 g/mL, Barite 4.1 g/mL or a named non-API grind
- Quantity and unit: sacks, t or bbl
- Packaging: bulk, bulk bags or sacks
- Delivery point: country and port or site
- Documents: CoA, SDS and API Monogram where relevant
A certificate of analysis (CoA) reports the lot against the requirement table, and the API Monogram is voluntary licensing that needs an API Spec Q1 quality system. Buyers compare additive suppliers on these documents.
Barite packaging and marking#
API Spec 13A Addendum 2 lists bulk pneumatic delivery, bulk bags, multi-wall paper sacks and cardboard boxes, and requires marking with the grade label, net mass and a lot traceable to facility and country of origin. Each pallet carries at most 2,000 kg (4,400 lb) net and stands at most 2.0 m (80 in) high unless agreed.
A request is complete when it states packaging and API 13A grade in a quote together with the quantity and delivery point.
Where barite is mined and imported#
India led world barite mine production in 2025 with 3,000 kt of an estimated 8,700 kt excluding the United States (USGS MCS 2026, estimated).
The table below lists the USGS supply record.
| Item | Value | Year |
|---|---|---|
| World mine production excluding the US | 8,700 kt | 2025e |
| India | 3,000 kt | 2025e |
| China | 2,200 kt | 2025e |
| Morocco | 1,000 kt | 2025e |
| Kazakhstan | 700 kt | 2025e |
| Iran | 300 kt | 2025e |
| Mexico | 300 kt | 2025e |
| US imports | 2,300 kt | 2025e |
| Share of US barite imports by source | India 39 %, China 21 %, Morocco 19 %, Mexico 14 %, other 7 % | 2021 to 2024 |
| US barite sold by crushers and grinders | about 2.3 Mt in 9 States | 2025e |
Ground barite enters the United States duty-free under HTS 2511.10.10.00, and other barite under 2511.10.50.00 pays USD 1.25 per t (US International Trade Commission, HTS, 2026).
Barite unit values in the public record#
The USGS put the average unit value of ground barite at USD 210 per t ex-works in 2025 (estimated), a dated public-record value, not a quote for any delivery.
The table below lists USGS unit values.
| Year | USD per t, ground, ex-works |
|---|---|
| 2021 | 167 |
| 2022 | 145 |
| 2023 | 218 |
| 2024 | 210 |
| 2025e | 210 |
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How Does Barite Compare with Other Weighting Agents?#
Barite is the reference weighting agent against which hematite, ilmenite, manganese tetroxide and calcium carbonate are compared, and the USGS names these four as its most common alternatives (MCS 2026). Less than 10 % of US barite sold goes to uses outside drilling fluids.
Celestite, iron carbonate and strontium carbonate appear in the literature as barite substitutes but are not widely used (USGS MCS 2026). Among weighting agents, barite sits between calcium carbonate and hematite in specific gravity.
Denser and acid-soluble alternatives to barite#
Hematite is chosen over barite for fewer solids by volume at the same density, manganese tetroxide for acid solubility and fine size, and calcium carbonate for acid solubility at low density.
The table below compares barite alternatives.
| Material | Chosen for | API Spec 13A |
|---|---|---|
| hematite | fewer solids by volume, acid-soluble | clause 8 grade |
| ilmenite | higher SG than barite | not covered |
| manganese tetroxide | acid-soluble, about 1 µm, formate fluids | not covered |
| calcium carbonate | acid-soluble, low density | not covered |
| cesium formate brine | solids-free density | not covered |
In barite vs hematite as weighting agents, the trade is solids volume against abrasiveness; in barite vs bentonite in drilling mud, it is density against viscosity.
Does barite dissolve in acid?#
No: barite is insoluble in common acids, while hematite, manganese tetroxide and calcium carbonate dissolve in acid.
Barite plugs and weighted pills#
Kill-weight fluid is made by adding barite or hematite to part of the mud, and barite is also the solid of barite plugs and weighted pills. Well cementing, including weighted spacers, is a separate field.