Photo of Euclase in Processed & Rough Form
Euclase is a mineral with a hardness of 8 out of 10 on the Mohs scale of mineral hardness [?]. These Monoclinicly structured gems are made of beryllium aluminum hydrosilicate, their full chemical compound being Be(Al,OH)SiO4.
Euclase is a silicate with a monoclinic crystal system. It is considered a very rare gem of light blue color.
It appears as long or short prismatic crystals, flattened and transparent.
It is colorless, white, green, or blue, commonly a pale aquamarine or green, but crystals of a very fine dark blue (from iron) have been found at the Miami mine in Zimbabwe. Crystals are often striated.
It is very hard, light, with one direction of perfect cleavage and conchoidal fracture. It is transparent to translucent with bright, vitreous luster. It is insoluble and fuses with difficulty.
Euclase occurs principally in granite pegmatites associated with topaz. It can also occur in alluvial placer sediments and geodes.
The finest crystals of colorless, blue and green gem-quality euclase have been mined near Ouro Prieto, Minas Gerais (Brazil). Crystals up to 5cm or larger have been found. Other sources in Kenya, Tanzania, Sanarka River (Soviet Republics), Ireland, Australia, and Park County, Colorado (USA)
It can be confused with topaz, aquamarine, beryl, and hiddenite, and is sometimes erroneously called "prismatic emerald."
Why is Euclase so rarely seen in jewelry?
Despite its beauty and high refractive index, euclase's perfect cleavage makes it extremely challenging to cut and wear. Most specimens are preserved for collectors rather than cut into gems. When faceted, it requires extremely careful handling.
What makes Brazilian Euclase unique?
Brazilian euclase, particularly from Minas Gerais, is known for its exceptional blue colors and transparency. These specimens often show more intense color than material from other locations and can reach larger sizes.
Why do some Euclase crystals appear colorless?
Pure euclase is naturally colorless; blue and green colors come from trace elements. Colorless specimens can be highly valuable if they show exceptional clarity and crystal form, particularly prized by mineral collectors.
How does Euclase compare to Aquamarine?
While both contain beryllium and can show similar blue colors, euclase has higher brilliance but much lower durability. Its refractive index is higher, creating more sparkle, but its perfect cleavage makes it far more fragile.
Are color-change Euclases real?
Some rare euclase specimens show subtle color changes between natural and artificial light. This phenomenon is most common in specimens from Zimbabwe, though the effect is typically less dramatic than in alexandrite.
What determines Euclase value?
For crystals, value depends on color intensity, transparency, and crystal form. For cut stones, color, clarity, and size are crucial, with intense blue specimens commanding highest prices. Exceptional specimens from historic locations carry premiums.
Why do some specimens fluoresce?
Many euclase crystals show distinctive fluorescence under UV light, particularly specimens from specific localities. This property can help in identification and adds interest for collectors, though it doesn't significantly affect value.
The specific gravity [?] for Euclase is 3.1, its refractive index [?] is 1.65-1.67, and its double refraction [?] is 0.019.
History
Its name derives from its quality of having perfect cleavage, leading Rene Hauy to call it after the Greek words for "fracture" and "easily." It is formed from the decomposition of beryl.
Industrial Usages
Euclase is occasionally faceted into gems with high brilliance. Because of its perfect cleavage, it is difficult to cut, but a number of faceted specimens exist, and are prized by collectors.
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