Calcite and AragoniteThis specimen quite clearly has two different minerals in it, but interestingly
Calcite and AragoniteThis specimen quite clearly has two different minerals in it, but interestingly they both have the same chemistry. The pink minerals are crystals of calcite, the thin crystals are aragonite. Both of those minerals have the same chemical formula; CaCO3.The minerals have different shapes because the atoms in each mineral are assembled in a different pattern. Both minerals crystallize from water and slightly different water chemistry will favor one mineral over another. Higher magnesium contents in water will stabilize aragonite, higher calcium contents will stabilize calcite. This change happens even though their chemistry is similar.Interestingly, life has figured out this structural difference. Many organisms make calcium carbonate shells and aragonite is slightly stronger than calcite. Aragonite has a hardness of 3.5-4, while calcite has a hardness of 3. Even though calcite is the stable mineral forming from the ocean today, many organisms make aragonite anyway.The light pink color of the calcite is most likely due to a slight bit of manganese included in the structure of that mineral.-JBBImage credit: http://bit.ly/28e7sL2Reference:http://www.minerals.net/mineral/aragonite.aspxhttp://abt.cm/1TVDiI7MineralMonday -- source link
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