Dolostone

 Identification: Dolostone is a sedimentary rock composed principally of the mineral dolomite CaMg(CO3)3. The mineral has a white, light brown or pink color, with a white streak.  The test for dolostone is the same as that for calcite, except that dolostone effervesces very slowly in cold dilute hydrochloric acid, and more vigorously in warm acid.
Occurrence: Dolostone is usually found closely associated with limestone deposits.
Use: Dolostone can be used for most of the same purposes as limestone except for making Portland cement, because in this process the magnesium (Mg) interferes with the setting properties of the cement .