Boleite

Boleite is a highly attractive, though uncommon, blue mineral that forms in very distinct crystal habits. Its crystals can be perfectly cubic, both in individual isolated crystals, and may be perched on fragile matrix. Boleite may also form together with the minerals Pseudoboleite and Cumengeite as epitaxial overgrowths, in mineralogically fascinating examples. These similar minerals form together in a single specimen with an inner cubic core of Boleite, and outer protruding portions either Pseudoboleite (additional protruding square faces) or Cumengeite (triangular faces in a star-like formation.)

Boleite has been found in several localities worldwide, however, its only significant source was the the Amelia Mine in Baja California, Mexico. To date, this is the only only locality that had produced this mineral in large, well-formed crystals, as well as the uncommon epitaxial overgrowths.

The matrix of Boleite crystals is often friable and can crumble. Matrix specimens are often stabilized with glue to prevent their crumbling. Boleite is named after its type locality at Boleo, Baja California, Mexico.

Most often as cubic crystals, which can be perfectly shaped. Crystals may have modified octahedral faces or corners. Also in intergrown cubic crystals, and in clusters of cubic crystals. Epitaxial overgrowths of pyramidal Cumengeite on Boleite crystal faces form 6-sided star-shaped crystal formations which may resemble a Star of David. Epitaxial overgrowths of cubic Pseudoboleite  on Boleite crystal faces form a cube with protruding rectangular faces on each of the six sides.

The crystal class of Boleite is generally classified as isometric; however, possible tetragonal symmetry has been detected in certain studies, leading to inconclusive results in its crystal group classification.

The premier locality for Boleite, which is also the type locality, is the Amelia mine, Santa Rosalia (Boleo), Baja California Sur, Mexico. This is the only area where Boleite occurs as relatively large crystals.

Boleite localities where it forms in microcrystals include the Lavrion District, Attikí Prefecture, Greece; the San Francisco Mine, Caracoles, Antofagasta Region, Chile; Challacollo, El Tamarugal Province, Chile; the Mammoth-Saint Anthony Mine, Tiger, Pinal Co., Arizona; and the Rowley Mine, Theba, Maricopa Co., Arizona.