Its namesake seas were the predominate form of seawater chemistry during the late Mesozoic, and are favored in times of lower magnesium concentration.
Its namesake seas were the predominate form of seawater chemistry during the late Mesozoic, and are favored in times of lower magnesium concentration. It has two metastable polymorphs, vaterite and aragonite,which have dihexagonal dipyramidal and orthorhombic structures, respectively, in contrast to the trigonal rhombohedral crystals of this mineral. The standard for the Mohs hardness of 3, examples of it with exceptional transparency are given the name "Iceland spar." Such crystals are notable for displaying strong birefringence. The primary constituent of limestone and marble, for ten points, name this mineral composed of calcium carbonate.
Its namesake seas were the predominate form of seawater chemistry during the late Mesozoic, and are favored in times of lower magnesium concentration.
{calcite}