Selenite crystals and siderite with pyrite pseudomorph base

Selenite crystals and siderite with pyrite pseudomorph baseLocale: Potos Mine, Santa Eulalia, Chihuahua, Mexico Approx dimensions: 4 x 3 x 2. 5" Approx weight: 490g (1 lb) This specimen is a sampler mix of minerals from the Potos Mine, with selenite and light to orange yellow siderite on a heavy base composed of several minerals. Selenite is the crystal clear form of gypsum, though the two terms are often used interchangeably. Selenite is one of the more common minerals to come from Mexico, which is known for

Locale: Potosí Mine, Santa Eulalia, Chihuahua, Mexico

Approx dimensions: 4 x 3 x 2.5"

Approx weight: 490g (1 lb)

This specimen is a sampler mix of minerals from the Potosí Mine, with selenite and light-to-orange-yellow siderite on a heavy base composed of several minerals. Selenite is the crystal-clear form of gypsum, though the two terms are often used interchangeably. Selenite is one of the more common minerals to come from Mexico, which is known for the nearby Naica locale. This selenite shows typical twinned and fishtail growth habits.

The heavy base is pyrite, pyrrhotite, and galena. The large hexagonal formation is characteristic of pyrrhotite, a mineral that looks quite similar to pyrite. Pyrite from the Potosí Mine is known to pseudomorph after pyrrhotite in this hexagonal formation, which appears to have occurred with this specimen. Pyrrhotite is supposed to have some slight magnetism, and this piece—like pyrite—does not seem too. Shining masses of pyrite grow on its surface and have rosette-like growth.

Near the 'top' back there is a chunk of dark gray mineral with cubic surface patterning I suspect to be galena because it commonly accompanies pyrite, pyrrhotite, and siderite from this locale. The galena has formed a small flat square tabular crystal coated in overgrowth, visible on the front of the specimen.

UV reactivity Under 365nm UV light, the selenite fluoresces an icy blue color in patchy areas of the back.

** Brittle warning: Selenite is soft and can easily break, flake, or bend. There are several crystals with curvature which I believe is damage that occurred to the specimen, not natural bending. Handle this specimen by the heavy base to avoid damage.