• An aragonite and calcite specimen in indirect sunlight. It is a chunky irregular-shaped piece with the top covered with semi-translucent white botryoidal growth.
  • Detail of the botryoidal growth, with fine blade-like structure to the spheres. The spheres grow on ridges of matrix, creating a complex surface with many nooks.
  • Another angle of the top of the specimen, covered with white botryoidal mineral growth.
  • The specimen held on-end, with different lighting on the botryoidal growth. The spheres have a soft matte surface.
  • Detail of slightly translucent white botryoidal growth, with cave-like holes between layers.
  • A side of the specimen with a brown matrix exposed with a white crust of the botryoidal aragonite on it. There are small spots of green mineral near the bottom.
  • The back of the piece, a light brown rough rock matrix with patches of a green mineral in it and veins of white mineral.
  • Scale image of the piece on a measuring mat, measuring about three inches long and two and a half inches wide.
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Botryoidal aragonite and calcite

Botryoidal aragonite and calcite

$22.00 USD
$22.00 USD
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Locale: Sidi Ayed, Fès-Meknès Region, Morocco

Approx dimensions: 3 x 2.5 x 2"

Approx size: 365g

 

Calcite and aragonite are polymorphs of one another, meaning that the same chemical composition (calcium carbonate) has crystallized into different crystal structures (trigonal and orthorhombic, respectively). Calcite and aragonite often grow together, and the two minerals are also frequent paramorphs of one another—a pseudomorph of the same chemical composition and retaining the original crystal shape but with different crystal structure, created through a change of conditions such as heat or pressure. There is understandably some confusion distinguishing what is calcite, versus aragonite, or a paramorph, or some hodgepodge of all of the above.

Which is all to say, this specimen falls somewhere in that ‘hodgepodge’ category. This piece is mostly botryoidal, meaning composed of small spheres that cover the surface. The spheres are textured and near-opaque with light near-white color. The specimen is attached to a rock matrix with a few small pockets of malachite, which is also commonly sourced from this region.

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