According to About.com, dolostone refers to rock that is composed primarily of the mineral dolomite, which forms when calcite limestone is altered underground. This chemical change, called dolomitization, results in a reduced volume and recrystalization of the stone, making it more porous. This process is not fully understood by sedimentary geologists.
The Kentucky Geological Survey describes dolostone as often having a "slightly sugary (saccharoidal) texture" and a tendency to turn to a buff or brown color as it weathers due to iron carbonate in the stone. It is harder and heavier than limestone and slower to bubble when exposed to dilute hydrochloric acid. Dolostone is commonly used for road aggregate, as agricultural limestone, in the making of rock wool, in the manufacture of magnesium and dolomite refractories, and as a component of natural cement. It is also used as a building material and as ornamental stone. Dolostone is important to the petroleum industry because of its natural porosity, which allows oil in the ground to travel more freely and form deposits, according to About.com.
About.com also explains that dolostone was first described in 1791 by a French mineralogist named Déodat de Dolomieu, who observed it in the southern Alps. Today, this range of mountains is called the Dolomites.