Sphalerite

Field of view: 5 mm. An euhedral crystal of sphalerite perched on quartz. The transparent brown trapezohedron is sphalerite. The crystal is transparent as its Fe content is very low. The rough surface at the right is attributed to growth hillocks by spiral dislocations. The transparent prisms at the basement are quartz crystals.

Recovered from an open space of a quartz vein in a moderate-temperature hydrothermal deposit in andesitic pyroclastics formed by dacite probably associated with volcanic activity of a caldera. Formed in the middle Miocene (15 Ma).

Sphalerite from this location was described in 1903.