Wednesday, 3 July 2013

Introduction to Malachite


MalachiteBasic copper carbonate. It is an ore of copper.

Crystal system

Monoclinic

Appearance

It occurs as rounded (mamillated) maws or encrustations, consisting of radiating or parallel aggregates of minute elongated crystals. It has striking stratification from quite bright to dark green. The stratifications are curved according to the outer surface of the mass. It is opaque or semiopaque.

Physical properties


It has a low hardness of about 4. like other carbonates. The refractive indices are n 1.655 fly 1.909, but are difficult to establish, both because the material is semiopaque, and because fly is very high, well above the range of ordinary refractometers. It has a density of about 3.8 g/cm.

Genesis

It is commonly formed by the action of atmospheric agents on copper mineral outcrops.

Occurrence

Large quantities of malachite are found wherever copper outcrops occur: in Chile, the United States, Zaire, Zimbabwe, Namibia, the Soviet Union, are Australia. But it is found almost everywhere in the form of small encrustations, together with azurite.

Malachite

The name is derived from the Greek matakhe, meaning "mallow," evidently because of the color.

Appearance

The color is always green, varying from a mid green which can be described as mallow green, to a very dark, even blackish green. These tones appear, as a rule, in alternate stripes (transverse to the length of the crystal), which are obviously successive layers of cometion and have an arrangement similar to that of the veins in other concretions, with broad curves, dome shapes, and undulations, generally following the direction of the outer surface of the stone. It has a fairly low hardness, but can acquire exceptional (though not very durable) polish. It a easily damaged by acids. Large blocks are used for slabs balusters, and other sculpted objects. It is also employed for mosaics, boxes, figurines, cabochons and beads.

Distinctive features

The green color, veining, shape of the veins, and polish make it unmistakable.

Occurrence



Ganesha malachiteIn the past, most malachite came from the Soviet Union (Urals), but nowadays large quantities are also obtained from Zaire, Zimbabwe, Namibia, Chile, the United States, and Australia.

Value

It is not often used as a gem and has a very low value. It is much admired, however, as an ornamental material and is quite highly priced for its category, especially when the attractiveness of the material is matched by fine workmanship.

Simulants and synthetics

It has not been imitated and is not produced synthetically.

Writer – Curzio Cipriani and Alessandro Borelli

No comments:

Post a Comment