Skip to content
SupplyList
Menu

Calcium carbonate

Calcium carbonate suppliers and sourcing guide

Calcium carbonate is the calcium salt of carbonic acid and the most concentrated common calcium source, at roughly 40% calcium by weight. It is either ground from natural limestone or other mineral and shell deposits, or made synthetically by precipitating it from lime with carbon dioxide or from calcium chloride. Brands buy it as a fine white powder or as a granulated grade for direct compression into tablets and chewables.

See suppliersWhat to ask for on the COA
Also known as
CaCO3 · E170 · Precipitated calcium carbonate · Ground limestone · Chalk
Facts checked
November 2026

Forms and grades of calcium carbonate

Suppliers sell different products under the same name. Specify the one you need.

  • Precipitated calcium carbonate (PCC)

    Made by precipitation, with tightly controlled particle size and generally lower levels of mineral impurities than ground grades.

  • Ground limestone (GCC)

    Mined limestone that is ground and classified; lead and other metals depend on the deposit, so source and testing matter.

  • Shell and algae-derived

    Calcium carbonate from oyster or egg shells or from calcified red algae, sold for natural-source label positioning; metals and identity of the source are checked per lot.

  • Directly compressible granulation

    Calcium carbonate granulated with a binder such as starch or maltodextrin so it can be pressed into tablets without a separate granulation step; the binder lowers calcium per gram.

  • Light and heavy powders

    Grades sold by bulk density, which affects capsule fill weight and how the powder flows and blends.

What to check on the COA

Compare each result with your own specification when the lot arrives.

Assay
Calcium carbonate content on the dried basis by complexometric (EDTA) titration, against a Food Chemicals Codex or USP specification.
Loss on drying
Moisture, which should be low; higher values point to poor storage or a carrier in granulated grades.
Acid-insoluble substances
Material that does not dissolve in dilute acid, mostly silica and clay from mined sources.
Lead and other metals
Lead, arsenic, cadmium and mercury by ICP-MS; this matters most for limestone, shell and algae sources.
Fluoride and magnesium and alkali salts
Compendial limit tests that flag mineral impurities from the deposit or process.
Particle size and bulk density
Laser diffraction or sieve analysis and tapped density, which drive mouthfeel in drinks and flow in tablet presses.

Storage, lots and expiry

Storage and shelf life

Calcium carbonate is stable and does not oxidize, but it should be kept in closed bags in a dry area off the floor, away from acids and strong odors that the fine powder can pick up. Granulated grades are more sensitive to humidity than plain powder because of the binder. Shelf life is set by the supplier's specification and is often long; retest moisture and micro on aged stock.

Lots and expiry dates

Record the source (precipitated, limestone, shell or algae), the assay and the lead result for each lot, and keep the particle size grade constant for tableting. A change of deposit or supplier can shift metals and density even when the assay stays the same.

Regulatory status

Facts from regulators and standards bodies, each linked to its source.

This is general information, not regulatory advice. Status differs by country and by how the ingredient is used, so check the rules for your product and market.

Calcium carbonate suppliers

Manufacturers and distributors whose own websites say they sell it.

We are checking calcium carbonate suppliers now

Every listing is checked against the supplier’s own website before it goes live, so this list fills in over the coming weeks. The specs and COA checklist above are ready today.

Sell calcium carbonate? Request a listing

Frequently asked questions

What forms of calcium carbonate can brands buy?

Common forms include precipitated calcium carbonate (PCC), ground limestone (GCC), shell and algae-derived, directly compressible granulation and light and heavy powders. Ask each supplier for the specification sheet of the exact grade they quote.

What should the COA for calcium carbonate include?

Expect assay, loss on drying, acid-insoluble substances, lead and other metals, fluoride and magnesium and alkali salts and particle size and bulk density, each with its method, specification and result for that lot.

How should calcium carbonate be stored?

Calcium carbonate is stable and does not oxidize, but it should be kept in closed bags in a dry area off the floor, away from acids and strong odors that the fine powder can pick up. Granulated grades are more sensitive to humidity than plain powder because of the binder. Shelf life is set by the supplier's specification and is often long; retest moisture and micro on aged stock.

What is the regulatory status of calcium carbonate?

21 CFR 184.1191 affirms calcium carbonate as GRAS, used in food with no limitation other than current good manufacturing practice. 21 CFR 73.70 lists calcium carbonate as a color additive that may be used to color dietary supplement tablets and capsules, in amounts consistent with good manufacturing practice. 7 CFR 205.605(a) lists calcium carbonate among the nonsynthetic substances allowed in or on processed products labeled organic. Health Canada's Multi-Vitamin/Mineral Supplements monograph for natural health products lists calcium carbonate among the source ingredients for calcium (Table 2).

More vitamins and minerals

All 75 vitamins and minerals

Sell ingredients to brands?

Request a free listing for the ingredients you make or distribute. No paid placement.

Request a listing