Examples from the Web for aragonite
The shell consists of carbonate of lime, under one or both of the forms known to mineralogists as calcite and aragonite.Colouration in Animals and Plants|Alfred Tylor
Like aragonite it is very frequently twinned, the compound crystals being pseudo-hexagonal in form.
Many calcareous fragments consist of aragonite, wholly or principally, and this mineral tends to be replaced by calcite.
Calcium carbonate may crystallize in either of two forms, calcite or aragonite.A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public|Frank Bertram Wade
Aragonite is the least stable form; crystals have been found altered to calcite.