Barite for drilling fluids: API 13A grades explained

By SilkStone Trading. Updated October 31, 2026.

Short answer

Drilling mud uses barite ground to API Specification 13A, the American Petroleum Institute standard for drilling fluid materials. API 13A has two barite grades: the standard grade with a specific gravity of at least 4.20, and a lower-density grade with a minimum of 4.10, often called 4.1 barite. SilkStone Trading supplies crude barite lump from Balochistan, Pakistan, at SG 4.20 or 4.10 for grinding to API 13A, and barite ground to API 13A, by the 20ft container.

Why drilling mud uses barite

Barite is heavy, so it's added to drilling fluid to raise the mud weight and control well pressure. According to the US Geological Survey, more than 90% of the barite sold in the US is typically used as a weighting agent in fluids for drilling oil and gas wells, and the US relies on imports for more than 75% of what it uses.

What grade of barite is used in drilling mud?

Barite for drilling mud is bought to API Specification 13A. Products sold as API 13A barite list these limits: specific gravity of at least 4.20, no more than 250 mg/kg of water-soluble alkaline earth metals measured as calcium, no more than 3.0% by weight left on a 75-micron (US No. 200) sieve, and no more than 30% by weight of particles under 6 microns. Ask your supplier for results against each of these, not just the SG.

SG 4.20 vs SG 4.10 barite

API 13A added a 4.1 grade for barite with a specific gravity of at least 4.10. Product data for 4.1 barite shows the same limits for soluble alkaline earth metals, residue and fine particles as 4.20 barite; the difference is the minimum density. Lower-SG barite takes more material to reach the same mud weight. Which one you buy depends on your fluid program and what your customer accepts.

Crude barite lump vs ground barite

Grinding mills buy crude barite lump and grind it to API 13A themselves. Mud and fluids companies that don't grind buy barite already ground to API 13A. We sell both: crude barite lump at SG 4.20 or 4.10 for grinding to API 13A, and barite ground to API 13A.

What should a barite quote include?

A typical analysis should come with the quote: specific gravity, BaSO₄ %, Fe, water-soluble alkaline earth metals as calcium, and lump size for crude lump. Then the lot you actually buy should be assayed before loading. We send the typical analysis with every barite quote, assay each lot, and welcome your own inspector, for example SGS or Bureau Veritas.

What HS code is barite?

Natural barium sulfate (barytes) is HS 2511.10. In the US tariff schedule, ground barite is 2511.10.1000 and crude barite is 2511.10.5000. USGS lists the normal duty rates as free for ground barite and $1.25 per metric ton for crude barite. Check current additional duties for your country of origin with your customs broker.

Where Pakistani barite comes from

USGS lists Pakistan among the world's barite-producing countries. Ours comes from Balochistan and ships from Karachi in 20ft containers, with bulk on request, FOB Karachi or CIF US and Gulf ports. Every shipment goes with a certificate of origin, analysis report and packing list.

Sources

Rules change. Check the current version of each source and confirm with your customs broker before you ship.