Jewel__A_Celebration_of_Earth_s_Treasures

202 SILICATES

Oval brilliant | Colour variety | This

fine-quality, highly transparent yellow

enstatite gemstone has been faceted in

a modified brilliant oval cut.

Enstatite crystal | Rough | Enstatite is

rarely found in well-formed crystals such

as this, a large specimen that shows the

mineral’s prismatic form.

Rough specimen | Rough | This piece of

enstatite demonstrates its occurrence as a

rock-forming mineral. It could be cut and

polished, but would not yield a gem.

Polished enstatite pebble | Cut | This tumble-polished baroque

of enstatite shows the multicoloured patterning – in this case in a

patchwork-like formation – that sometimes occurs when enstatite

is found in conjunction with other minerals.

W

hile it is an important rock-forming mineral, enstatite’s major commercial

use is as a gemstone, in colourless, pale yellow, or pale green hues.

The most popular colour is the emerald-green variety, known as chrome-

enstatite, and its green colour is caused by traces of chromium – hence the name. All

colours are relatively rare, and gemstones are faceted or cut en cabochon. Mysore,

India, produces star-enstatite; Canada produces iridescent enstatite; and the gem

gravels of Myanmar and Sri Lanka yield good-quality facet-grade material.

Specification

Chemical name Magnesium silicate | Formula Mg 2 Si 2 O 6

Colours Colourless, yellow, green, brown, black | Structure

Orthorhombic | Hardness 5–6 | SG 3.2–3.3 | RI 1.66–1.67

Lustre Vitreous | Streak Grey to white | Locations India,

Canada, Myanmar, Sri Lanka

Enstatite

△ Piece of massive enstatite suitable for tumble-polishing

Plane of fracture

Intergrown enstatite

crystals

Enstatite in space

Minerals of the early solar system

The presence of enstatite in certain

meteorites implies that it was one

of the first-formed silicate minerals

in the solar nebula that created the

Earth and solar system. It occurs

in about 10 per cent of meteorites

known as chondrites. These are

agglomerations of mineral grains

that never became part of large

enough bodies to undergo melting

and re-crystallization. It is thought

that they were first formed near

the centre of the solar system.

Stony iron meteorite Known as chondrites,

this variety of iron meteorite sometimes carries

quantities of enstatite.

Cat’s-eye cabochon | Cut | Enstatite is

one of the minerals that will sometimes

produce a star or “cat’s eye” when polished

en cabochon, as in this example.

Polished surface

202-203_PRO_Enstatite-Diopside.indd 202 18/05/2016 11:40