THE MINERAL EUCLASE
- Chemistry: BeAlSiO4OH, Beryllium Aluminum Silicate Hydroxide.
- Class: Silicates
- Subclass: Nesosilicates
- Uses: Gemstone and as mineral specimens.
Specimens
The crystals of euclase are commonly prismatic with slanted termination faces. Unlike other monoclinic minerals whose crystals will commonly look like higher symmetry crystals, euclase's crystals are distinctly monoclinic due to the slanted termination. Nice crystals of euclase are much sought after by collectors.
Euclase is found in granitic pegmatites with other gem minerals such as topaz and beryl. It is easily identified by its crystal form which can only be confused with barite or celestite but is the wrong environment for these sulfate minerals. Topaz has a completely different cleavage (basal) than euclase (prismatic). Transparent albite is softer. Euclase weathered out of source rock and transported down stream can end up being found in placer deposits with gold.
Euclase gets its name from its easy cleavage, euclase simply means easily cleaved. This is a problem for gem cutters who need to be careful of splitting an unfinished gem. It also detracts from it durability which limits its acceptance as a common gemstone. Another negative is its splotchy color distribution, but a skilled gem cutter can work a stone to its own advantage. Euclase is a real treasure in well formed crystals and in colorful gemstones.
PHYSICAL CHARACTERISTICS:
- Color includes colorless, blue-green, blue, yellow, light green and rarely purple.
- Luster is vitreous.
- Transparency: Crystals are transparent to translucent.
- Crystal System is monoclinic; 2/m
- Crystal Habits include stubby prismatic crystals with non-symmetrical slanted terminations.
- Cleavage is perfect in one direction (prismatic), poor in two other directions.
- Fracture is conchoidal.
- Hardness is 7.5
- Specific Gravity is 3.09 - 3.11 (slightly above average)
- Streak is white.
- Other Characteristics: Almost always striated lengthwise.
- Associated Minerals include micas, quartz, topaz, beryl, gold,
pericline and some feldspars. - Notable Occurrences include Ouro Preto and other areas within Minas Gerias, Brazil; Kenya; Tanzania; Ural Mountains, Russia; Germany and with emeralds in the famous mines of Columbia.
- Best Field Indicators are crystal habit, good cleavage, striations, hardness and color.
 Amethyst Galleries' Mineral Gallery MINERALS |
EUCLASE specimen euc-1
$ 60.00
$ 60.00
Dims: 0.8" x 0.6" x 0.6"(2.0 x 1.5 x 1.5 cm)
Wt: 8.4 g
Equador, Rio Grande do Norte, Brazil
This specimen consists of a single crystal of Euclase, a mineral that is remarkably similar in composition to beryl. It has a white-to-pale-blue coloration and is translucent due to highly concentrated internal fracturing. There is a definite crystal form, denoted by its hexagonal cross-section and 3 readily visible prism faces. However, the prism faces are extremely disjointed and are only discernable by finding the angle at which light will reflect off of them. The crystal has a vitreous luster.
euc-1 ($ 60.00)
Equador, Rio Grande do Norte, Brazil
EUCLASE specimen euc-2
$ 40.00
$ 40.00
Dims: 0.4" x 0.2" x 0.2"(1.0 x 0.5 x 0.5 cm)
Wt: 1.2 g w/ foam base
Equador, Rio Grande do Norte, Brazil
Though incomplete, this little Euclase crystal shows excellent form and good clarity. It is a blue-white color with patches of pale blue, and looks like half of a thick, square tabular crystal. The back of the specimen shows that it was broken off of either the crystal itself or a host rock of some sort. It has a vitreous luster and is transparent, although some cloudy inclusions cause interference. A lone, clear quartz crystal protrudes from the right side of the specimen, growing near and almost parallel to one of its edges. There is no host rock, and the specimen is attached to a foam base that fits into a plastic specimen box.
euc-2 ($ 40.00)
Equador, Rio Grande do Norte, Brazil
EUCLASE specimen euc-3
$ 50.00
$ 50.00
Dims: 0.7" x 0.5" x 0.4"(1.8 x 1.5 x 1.0 cm)
Wt: 2.6 g
Equador, Rio Grande do Norte, Brazil
Though this little Euclase thumbnail specimen is incomplete, those parts of it that are intact have excellent crystal form, with clean faces and edges. It is made up of a portion of a crystal whose shape I cannot quite identify, and is a blue-white color, with small spots of more pronounced, pale blue. It has a vitreous luster and is translucent, showing hints of transparence that are interrupted by heavy internal fracturing. It attaches to a plastic specimen box by means of a sticky, removable wax.
euc-3 ($ 50.00)
Equador, Rio Grande do Norte, Brazil
EUCLASE specimen euc-4
$ 45.00
$ 45.00
Dims: 1.2 x 0.9 x 0.6" (2.9 x 2.2 x 1.6 cm)
Wt: 0.4 oz. (11 g)
Equador, Rio Grande do Norte, Brazil
This thumbnail piece consists of an aggregate of heavily intergrown Euclase crystals. These crystals are generally in only fair condition, as most of the exposed edges are damaged or broken. The largest has apparent dimensions of 0.3 x 0.3 x 0.2" (8 x 8 x 5 mm) Where visible, they appear to have good monoclinic prismatic form and the standard vitreous luster. Their color ranges from nearly colorless to a moderately deep blue with a hint of green. All appear to be at least dimly transparent, though internal fractions affect their clarity. Several small quartz crystals permeate this aggregate, but there is no real base or host material present.
euc-4 ($ 45.00)
Equador, Rio Grande do Norte, Brazil
EUCLASE specimen euc-5
$ 37.50
$ 37.50
Dims:0.8x0.6x0.5" (2.0x1.5x1.3 cm)
Wt: 0.2oz. (6g)
Equader, Rio Grande do Norte, Brazil
This thumbnail specimen is an intergrown cluster of euclase crystals. Most of these crystals are colorless, but there are a couple of dark violet places in the cluster. Most of the crystals in this cluster show some damage; however, one doubly terminated crystal at the top of the specimen is intact. The largest crystal is just over 0.2" (0.5cm) in length.
euc-5 ($ 37.50)
Equader, Rio Grande do Norte, Brazil
EUCLASE specimen euc-6
$ 40.00
$ 40.00
Dims: 0.87x0.69x0.37" (2.22x1.75x0.93cm)
Wt: ?oz (?g)
Equador, Rio Grande do Norte, Brazil
This is a typical euclase specimen, with crystals exhibiting splotchy colors of a pretty deep aqua blue or colorless but appearing white due to internal fractures. The crystals are transparent, with the blue ones having the most clarity. Many of the crystals are striated, and others show complex growth patterns that obscure the striations.
euc-6 ($ 40.00)
Equador, Rio Grande do Norte, Brazil
EUCLASE specimen euc-7
$ 90.00
$ 90.00
Dims: 0.89x0.63x0.71" (2.26x1.60x1.81cm)
Wt: 0.31oz (8.8g)
Equador, Rio Grande do Norte, Brazil
This specimen is dominated by a single large crystal of euclase, although there are several small crystals and some patches of a feldspar present. The euclase crystal is mostly transparent and colorless, but there is a small patch of pale aqua-blue, and a sharply defined section of deep translucent aqua color. This section appears to be the same crystal, as the form and striations are continuous between that section and the bulk of the crystal. The clarity of the euclase is marred by numerous internal fractures. Still, this is a nice euclase specimen and is essentially undamaged.
euc-7 ($ 90.00)
Equador, Rio Grande do Norte, Brazil