noun.
An orthorhombic mineral form of crystalline calcium carbonate, dimorphic with calcite.
The Century Dictionary and Cyclopedia
noun.
Calcium carbonate crystallizing in the orthorhombic system.
the GNU version of the Collaborative International Dictionary of English
noun.
A mineral identical in composition with calcite or carbonate of lime, but differing from it in its crystalline form and some of its physical characters.