CALIFORNIAN JADE (VESUVIANITE)

Description:

Several names have been given to this mineral: californite, vesuvianite or idocrase. It is now recognized as vesuvianite by the CNMMN of the IMA. The mineral's name vesuvianite, given by Werner in 1795, was for its occurrence at  Mount Vesuvius, near Napoli (i.e., Naples ), Italy , where it was found in metamorphosed limestone blocks that were engulfed within the lava.  The name idocrase, given by Haüy in 1796, was based on the Greek and means mixed form, an allusion to its crystals showing a mixture of other mineral forms. The name californite was given to this material by the famous mineralogist and gemologist George Frederick Kunz, who was long associated with Tiffany and Company of New York City.

The mineral forms as a result of contact metamorphism on impure limestones and is usually found with other exotic minerals. Most of the gemrock material is some shade of green; some vesuvianite is of one or some combination of the following colors:  white, yellow, reddish brown, lilac or even bluish. It occurs in compact, massive varieties. A blueish variety is known as cyprine, the blue is due to impurities of copper. Californite is a name sometimes used for jade-like vesuvianite, also known as California-, American- or Vesuvianite-jade. Xanthite is a manganese rich variety. Crystals are transparent to translucent, they give vitreous or greasy to resinous luster.

Californite or Californian jade is a somewhat rare and beautiful mineral that can rival many other minerals for interest among mineral collectors. It often has streaks or irregular speckles of one or more colours mentioned above. It is widely used as a substitute for jade. The mineral forms fine gemstones for jewelry as well as fine carvings of rocks.

Some notable localities of this mineral include Asbestos, Quebec, Canada; California and the New England region of USA; Mt Vesuvius, Italy; Ural Mountains, Russia and Switzerland.

Characteristics:

Chemistry: Ca₁₀Mg₂Al₄(SiO₄)₅(Si₂O₇)₂(OH)₄, Calcium Magnesium Iron Aluminum Silicate Hydroxide

Class: silicates

Hardness (Mohs scale): 6.5 – 7

Density: 3.28 – 3.55

Crystal system: tetragonal

Crystal habit: prismatic crystals with an overall square cross-section

Transparency: transparent to translucent

Luster: vitreous to greasy to resinous

Cleavage: poor, in one direction lengthwise