3" Hematite Pseudomorph after Siderite on Smoky Quartz - Colorado

Hematite is a fairly common mineral, typically responsible for the red-brown colorations found in other minerals and rocks. Its chemical composition is Fe2O3, occasionally containing small amounts of titanium (variable formula (Fe,Ti)2O3). Much of the time, non-crystalline hematite specimens are the result of a transformation from limonite following loss of water.

Smoky quartz is a grey-brown to black variety of quartz. This common name is derived from the appearance of smoke within the quartz crystal. Depending on the location and the chemicals present during formation, smoky quartz can appear opaque black, but it is typically translucent to some extent. It is believed that the quartz gains this color from a combination of natural irradiation and aluminum impurities.