This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Dolomite (magnesian limestone) contains about 30 per cent. of carbonate of lime, 22 per cent. of carbonate of magnesia, and about 48 per cent. of carbonic acid. It may furnish a pure carbonic acid gas, but also shares the impurities of the other carbonates. In large layers, as white, grey and brown dolomite, it is found extensively, and in Europe not unfrequently used in the manufacture of carbonated beverages; however, in the United States other carbonates are so abundant and cheap, that its use is entirely excluded. The purer sorts of dolomite are used for making Epsom salt, other kinds for hydraulic lime, etc. It is easier decomposed by muriatic than by sulphuric acid and requires heat.