The Limestone, with the CAS registry number 1317-65-3, is also known as Calcium monocarbonate. Its EINECS registry number is 207-439-9. This chemical's molecular formula is CaCO₃ and molecular weight is 100.09. What's more, both its systematic name  is called Calcium carbonate. This chemical's classification code is Tsca Uvcb. It is odorless and white to tan powder. Limestone is a sedimentary rock composed largely of the minerals calcite and/or aragonite, which are different crystal forms of calcium carbonate.

Physical properties about Limestone are: (1) Melting Point: 825 °C; (2) Boiling Point: 2850 °C; (3) Density: 2.93 g/cm³.

When you are dealing with Limestone, you should be very careful. This chemical is irritating to respiratory system, skin and may cause inflammation to the skin or other mucous membranes. Besides, it risks of serious damage to eyes. Therefore, you should wear suitable protective clothing, gloves and eye/face protection. And in case of contact with eyes, you should rinse immediately with plenty of water and seek medical advice.

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