Rock Crystal

This is a gemmy and very interesting rock crystal quartz from Joaquim Felício, where the very steep rhombohedral faces are well developed, resulting in an overall shape that is very similar to a Muzo habit. In this case the rhombohedral faces lack the striation typical for the Muzo habit. Instead, the surface of the faces is covered with peculiar horizontal, parabolic indentations that all point in the same direction, reflecting the handedness of the crystals.

Remarkably in this quartz crystal from Joaquim Felício, the very steep rhombohedral faces have almost completely replaced the m-faces and occupy three of the six sides of the prism, called Ψ. The Ψ-faces are typically covered with numerous arrowhead-shaped indentations that are growth patterns, not etching patterns.

Furthermore other uncommon trapezohedron “x” faces are well developed. They form oblique stepped striations on alternating prism m-faces. Other smaller forms are also present. Similar old material is known from Joaquim Felício (Minas Gerais), but no detailed information is given for this sample.

Acquired in 1981 by Jan Sibtsen, #3696.

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