Young aragonite

The source materials for both the modern calcareous sands and young calcarenites of Bermuda are characterized by a complex metastable carbonate assemblage of skeletal aragonite, magnesian calcite, and calcite. The limestone... 

Biocoral is composed of crystaUine calcium carbonate or aragonite, the metastable form of calcium carbonate. The compressive strength of Biocoral varies from 26 (50% porous) to 395 MPa (dense) and depends on the porosity of the ceramic. Likewise, the modulus of elasticity (Young s Modulus) of Biocoral varies from 8 (50% porous) to 100 GPa (dense) [Biocoral, 1989]. 

Because of the high ceramic volume fraction, the mechanical properties of the shells are mainly determined by those of the ceramic. The ceramic component is aragonite, a rhombic crystal modification of calcium carbonate CaCOa, forming prismatic crystals. Young s modulus of aragonite is approximately 100 GPa, its fracture toughness is rather low, with a value of about 0.5 MPai/in. 

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