aragonite is the least stable form; crystals have been found altered to calcite.
aragonite, a mineral formed of calcium carbonate crystallized in the rhombic system; specific gravity 2.94 (compare Calcite).
Many limestones are rich in aragonite, but this in course of time tends to recrystallize as calcite.
aragonite is the more unstable of the two modifications of calcium carbonate.
Like aragonite it is very frequently twinned, the compound crystals being pseudo-hexagonal in form.
The thermal springs of Carlsbad deposit spherical concretions of aragonite, forming masses known as pisolite or Sprudelstein.
Many calcareous fragments consist of aragonite, wholly or principally, and this mineral tends to be replaced by calcite.
aragonite occurs in very small masses, of a light yellow color and fibrous structure, between layers of serpentine.
Thus calc spar is a common name for calcite, heavy spar for barite, needle spar for aragonite, and so on.
Being isomorphous with aragonite, it crystallizes in the orthorhombic system, but simple crystals are not known.
A usually white, yellowish, or pink orthorhombic mineral that can occur in many different colors. Aragonite occurs as acicular (needlelike) or tabular crystals, or as fibrous aggregates. It is found in gypsum deposits, at the tips of calcite crystals, in mollusk shells and pearls, and in living reef structures. It is a polymorph of calcite. Chemical formula: CaCO3.