Friday, August 22, 2014

Limestone vs. Dolomite vs. Dolostone

Some of my posts concerning the Lemont, IL, area mentioned "limestone." I have learned that I should have used the term "dolostone." Both are carbonate rocks (the molecules include CO3) and are very similar in appearance and usages. Limestone is a sedimentary rock formed from the mineral calcite. Calcite has the chemical formula CaCO3. Dolomite is the mineral that is formed when calcite is modified by magnesium-rich groundwater. The chemical formula is (CaMg(CO2)3). Dolomite was also used to refer to the rock formed from dolomite. Now geologists are switching to the term dolostone for rock made with dolomite to remove the confusion of using the term dolomite for two different meanings. But many existing texts and documents still refer to the rock as dolomite.

Dolostone is a little harder than limestone---3.5-4 vs. 3 on the Mohs Hardness Scale. In fact, calcite is the mineral that defines the hardness level of 3. And dolostone does not react (effervesces) as vigorously with dilute hydrochloric acid.

Both limestone and dolostone are used in construction for crushed rock, dimensional stone, and heated in a kiln (calcined) to create cement. And both are used to neutralize acid in the chemical industry, in stream restoration projects, and as a soil conditioner.

No comments:

Post a Comment