Aragonite and the more common mineral Calcite are polymorphous to each other. Although Aragonite and Calcite contain the same chemical composition, they differ in their crystal structure. Aragonite forms orthorhombic crystals, whereas Calcite forms trigonal crystals.

These 2 specimens look totally different from one another, yet if you look at the smaller piece, it has heaps of orthorhombic crystals compared to the single orthorhombic crystal with the bigger piece.

I acquired a small light brown round piece from Crystal Castle when on a road trip up to Byron Bay around Easter in 2015. This chunky specimen came from Greg at Blue Gems at the August 2016 Sydney Crystal Show.

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