In the past, the term "dolomite" was applied to both the mineral and the rock. The term "dolomite" is here restricted to the mineral, and the term "dolostone" is restricted to the rock.
Dolostone is a sedimentary rock composed chiefly of the mineral dolomite, which is magnesium calcium carbonate. It is closely related to limestone, both physically and chemically; in fact, when the magnesium content decreases, it is often referred to as magnesian or dolomitic limestone. Dolostones often exhibit a sugary (saccharoidal) texture and commonly weather to a buff or brown color caused by iron carbonate in the rock. Dolostone effervesces very slowly in dilute hydrochloric acid and is slightly heavier and harder than limestone. The most extensive deposits of dolostone in Kentucky occur in a north-south belt extending from Oldham County to Marion County and from Wayne County toward Lewis County. Geologists have referred to these strata as the Laurel and Brassfield Dolomites of Silurian age and the Renfro Member of the Borden Formation of Mississippian age, respectively. In the subsurface in Green and Taylor Counties, the Laurel is a good oil reservoir rock and is called the "Blue sand" by drillers. The "Corniferous" is another drillers' term for oil-bearing Silurian and Devonian dolomitic rocks in eastern Kentucky.
Dolostone is used as a building and ornamental stone; for road aggregate, and as agricultural lime; in the making of rock wool; as a flux in the production of pig iron in the blast furnace; for the making of natural cement; and in the manufacture of magnesium and dolomite refractories. For more information about limestone and dolostone, see Limestone section.