Aragonite and calcite with botryoidal side

Aragonite and calcite with botryoidal sideLocale: Sidi Ayed, Fs Mekns Region, Morocco Approx dimensions: 3 x 2. 75 x 2" Approx size: 480g (1 lb) 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 anothera pseudomorph of the same chemical

Locale: Sidi Ayed, Fès-Meknès Region, Morocco

Approx dimensions: 3 x 2.75 x 2"

Approx size: 480g (1 lb)

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 some hodgepodge of the above.

Which is all to say, this specimen falls somewhere in that ‘hodgepodge’ category. It appears aragonite formed over calcite points which then partially dissipated, leaving some hollow between layers. On the other side, the aragonite has formed more botryoidal growth composed of blade-like growth. There are dark greenish spots of another mineral embedded in the matrix.