Aragonite
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Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate, the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation from marine... Wikipedia
Cleavage: Good on, Poor on
Color: Can come in a variety of colors, but commonly red or white
Crystal habit: Commonly dendritic or pseudo-hexagonal; can also be acicular, tabular, prismatic, coral-like
Crystal system: Orthorhombic
Fracture: Subconchoidal
Luster: Vitreous, waxy, resinous
Solubility: Soluble in acids, and saltwater (but takes longer)