CRISTOBALITE
Specimen crb-5

Dims: 1.7 x 1.5 x 1.0" (4.3 x 3.8 x 2.5 cm)

Wt: 1.91 oz. (54.2 g)

Vechec, East Slovakia, Slanske Vrchy Mountains, Slovak Republic

This unusual specimen consists of an igneous base rock on which several round Cristobalite nodules rest. These nodules do not exceed 0.1" (3 mm) in diameter but are in excellent condition, showing only a small amount of damage. They show no appreciable tetragonal form, but their orbicular form denotes its crystalline tendencies. The orbs have a milky-white color and a dull, waxy luster, and are translucent. They are accomapanied by several tiny tridymite blades, several of which are broken. These have a brighter white color and have good pseudo-trigonal bladed form.

Dims:1.3x0.7x0.6" (3.3x1.8x1.5 cm)

Wt: 0.9oz. (24g)

Vechec, Slovakia

The top surface of this specimen is sprinkled with minute crystals of cristobalite. Under a loupe these crystals appear to be in the form of trapezohedrons, although the true form is tetragonal. It is possible, for cristobalite is known to assume a pseudocubic habit. I cannot be sure of the shape, however, for the crystals are too tiny to examine closely.

Dims:1.2x0.6x0.5" (3.0x1.5x1.3 cm)

Wt: 0.5oz. (15g)w/box

Vechec, Slovakia

The granular surface of this thumbnail specimen is liberally sprinkled with whitish crystals of cristobalite. These tiny crystals show excellent pseudocubic habit. Cristobalite is actually tetragonal in form. Also present on this specimen are tiny rounded nodules of an unknown black mineral.

Dims: 4.0x2.9x1.9" (10.3x7.5x4.8cm)

Wt: 9.8 oz. (278g)

Siskiyou, California, USA

This is an excellent specimen of cristobalite, as two large (and two small) radial clusters in an obsidian host rock. The contrast is excellent. The cristobalite shows a radial pattern but does not fill the cavities. Close examination (with a loupe) shows a peppering of some black mineral both in the cristobalite and on the surface, and there is another white mineral (likely another form of silicon oxide) on the exposed surfaces of the cavities. This second white mineral has a form of hands (with various numbers of fingers) of opaque white and rounded growths, mostly flat against the host. These clusters do sparkle like quartz, and may simply be quartz. In addition, there are several tiny and quite lovely very thin blades of some mineral (looks like wulfenite) on the surface.

Dims: 3.62x3.04x2.04" (9.19x7.71x5.18cm)

Wt: 9.43oz (267g)

Siskiyou, California, USA

Like other cristobalite specimens from this location, this one has white cristobalite crystals lining cavities in black obsidian. There is a radial growth pattern, and the mineral does not fill the cavities. A loupe reveals the presence of at least three other minerals: tiny fingers of dull white translucent something (I suspect quartz or another silicon oxide), a dusting of tiny black crystals (too small to identify), and some orange or brown blades that look like wulfenite.