OSHA PEL: Total Dust: 15 mg/m³; Respirable Fraction: 5 mg/m³
ACGIH TLV: TWA (nuisance particulate) 10 mg/m³ of total dust (when toxic impurities are not present, e.g., quartz <1%)

Calcium carbonate, with the cas register number 471-34-1, also can be called Carbonic acid calcium salt ; Marble ; and Limestone. Calcium carbonate is a chemical compound with the formula CaCO₃. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime, and is usually the principal cause of hard water.

Physical properties about Calcium carbonate are: (1)#H bond acceptors:3 ; (2)#H bond donors: 2; (3)Molecular Weight: 100.087 g/mol; (4)EINECS: 207-439-9; (5)Flash Point: 169.8 °C; (6)Enthalpy of Vaporization: 63.37 kJ/mol; (7)Boiling Point: 333.6 °C at 760 mmHg; (8)Density: 2.93 g/mL at 25 °C(lit.); (9)Vapour Pressure: 0.00856 mmHg at 25 °C; (10)Melting point: 825 °C

Preparation of Calcium carbonate: The vast majority of calcium carbonate used in industry is extracted by mining or quarrying. Pure calcium carbonate (e.g. for food or pharmaceutical use), can be produced from a pure quarried source (usually marble).Alternatively, calcium carbonate is prepared from calcium oxide. Water is added to give calcium hydroxide, and carbon dioxide is passed through this solution to precipitate the desired calcium carbonate, referred to in the industry as precipitated calcium carbonate (PCC)
CaCO₃ → CaO + CO₂
CaO + H₂O → Ca(OH)₂
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Uses of Calcium carbonate: Calcium carbonate is widely used in both its pure and its impure states. As marble chips, it is sold in many sizes as a filler for artificial stone, for the neutralization of acids, and for chicken grit. It is used to produce viscous solutions or dispersions, to impart body, improve consistency, or stabilize emulsions, including suspending and bodying agents, setting agents, jellying agents, bulking agents, stabilizers and thickeners.

When you are using this chemical, please be cautious about it as the following:
In case of contact with eyes, rinse immediately with plenty of water and seek medical advice;
Wear suitable protective clothing, gloves and eye/face protection;
Wear suitable gloves and eye/face protection;

You can still convert the following datas into molecular structure:
(1)InChI=1S/CH2O3.Ca/c2-1(3)4;/h(H2,2,3,4);/q;+2/p-2;
(2)InChIKey=VTYYLEPIZMXCLO-UHFFFAOYSA-L;
(3)Smiles=C(=O)([O-])[O-].[Ca+2]

The toxicity data is as follows: