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Pocketmags Digital Magazines
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Pocketmags Digital Magazines

Adding Beauty to Ancients and Shells

Aragonite

The mostcommon carbonate is calcite, calcium carbonate. It has acompanion in aragonite, which iscomposed of the same chemistry. Since both have exactly the same chemical molecules in the same ratios, the two are called paramorphs. The diTherence in paramorphs is internal, with each presenting diTherent crystal structures. Calcite forms six-sided hexagonal crystals while aragonite forms four-sided orthorhombic beauties. To confuse things further, aragonite has a great penchant for forming twins that look exactly like hexagonal crystals.

Itcommonly forms in twins that join to form a six-sided crystal called a sixling, which may look like calcite. These aragonite sixling twins are pseudohexagonal. The key is pseudo, which means false. Aragonite is lesscommon than calcite, but in the organic world it is verycommon and very important because it is an integral part of most seashells, pearls, and ancient fossils, especially ancient ammonites. Aragonite and calcite form under low-temperature conditions, but Aragonite is a little less stable. After it forms, it does not take much for it to rearrange its structure and become calcite. For example, banded onyx, which iscommon around hot springs, oThen forms as aragonite but then tends to alter into calcite once cooled. This explains why we use the term calcite onyx.

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Beckett Rock & Gem July 2019, Aragonite & Ancients : Serving to Enhance Ammonites, Canadian Diamonds, Captivated By BirthStones, And More....