Aragonite and calcite Siderite due to its distinctive radial

due to its distinctive radial starburst pattern on a dark chocolate-brown and red-tinted background

This specimen from Santa Eulalia has modified rhombohedral calcite crystals on a brown iron-oxide matrix

or some hodgepodge of all of the above

similar to quartz geodes

Aragonite and calcite Siderite due to its distinctive radialLocale: Sidi Ayed, Fs Mekns Region, Morocco Approx dimensions: 3. 75 x 2. 5 x 2 Approx size: 700g (1. 5 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