We will tell about a very beautiful and valuable stone, which has an attractive color and unusual patterns. Malachite is also known as “peacock stone”, “satin ore”, “copper green” or “azure-malachite”. Different names can be quite relative, or denoting a particular variety of malachite, but, nevertheless, they are all used both by professionals and everymen for the nomination of the stone. The name “malachite” is derived from Greek word “malake” meaning “mallow”. This association is due to the fact that the color of malachite resembles the color of leaves of this plant. The stone’s name is assumed to come from the Greek word “malakos” for “soft”. Perhaps this explanation of the name is due to the physical properties of the stone.
Formation of malachite
Malachite is formed in the oxidation zones of copper deposits – by dissolving of copper ore and the subsequent deposition of dissolved copper compounds in rock spaces and fractures. Malachite rarely forms individual crystals. This mineral is mostly represented by clusters, botryoidal and radial fibrous crusts, reniform aggregates (intergrowth of several crystals). Malachite often grows on cuprite and native copper in the form of crusts. In this case crystals will be acicular, thin prismatic, tabular, or spherocrystals. Malachite can also replace azurite crystals while keeping the external form of the replaced mineral. Malachite can form dripstones in karst caves or “bands” of ore-bearing limestones. As a rule, malachite is often found together with cuprite, chrysocolla, azurite, and other minerals, which are formed in the oxidation zones of copper. Note that eventually characteristic patina – which may be malachite by its composition – is formed on ancient bronze items.
Peculiarities of malachite structure
Malachite formations are opaque, and small crystals may slightly show through. In dense botryoidal intergrowths of several malachite crystals the color will be distributed rhythmically with alternation of light and dark bands. And thin-acicular aggregates (intergrowth of crystals) are characterized by even distribution of color. Stones obtained from dense dripstones, with a beautiful pattern, which is distributed zonally, are of great value for decorative works of art. Malachite can have a vitreous luster, and intergrowths of several crystals have characteristic silky or matt luster. Small crystals of malachite may be the finest needles, which are almost never formed separately. Expanding from the center, they form the whole radiant balls called spherulites. In the fractures or spaces where malachite is formed there can be a lot of such spherulites: they crowd and “encroach” on each other, forming entire botryoidal or reniform clots. Since copper content varies in different solutions, each of the newly growing layers of spherulites may be of either darker or lighter color. In those areas where the “needles” were formed more gently (or quietly), spherulites are more distinct. And in those areas where there were more changes in the content of copper, the layers become thinner, and the “needles” – invisible at all, but in such formations a complex pattern in the form of concentric bands appears.
Color peculiarities of malachite
Malachite is characterized by beautiful green color (its different shades) as well as an attractive texture of concentric rings. Malachite stones may have a light green or emerald green hue, with light blue or even black and green shimmering. Texture of malachite is presented by beautiful banded and undulated patterns, concentric rings, or radiant stellar distribution of color with alternating layers of different shades. So-called “eyed” malachite, also known as “peacock eye” is especially valued: the color in such a stone is distributed in the form of thin concentric rings. Radiant malachite is characterized by dark or grass-green hues, fine radiant structure and silky luster. Azure-malachite is a mixed type of mineral, which is a mixture of malachite itself and lapis lazuli. This stone is characterized by a beautiful green color with bluish shades. There is also turquoise malachite, which is loved by jewelers. The main feature of this stone is a beautiful pattern of complex curls (result from sinter formation). The smaller, more contrast and bizarre are these patterns (curls and bands), the higher the stone is valued. This malachite may have emerald blue or even turquoise hue. The internal texture of turquoise malachite can be parallel fibrous or concentric-zonal. There is also plush malachite, which is characterized by darker color, and radial fibrous structure. Compared with turquoise malachite, plush malachite is worse treatable.
The use of malachite
Malachite is a valuable gemstone. It is used for making jewelry, various accessories and interior decorative items. For example, stands and bases for table lamps or decorative interior sculptures, vases or caskets, ashtrays and accessories for stationery and other items can be made of malachite. In XVII-XIX centuries method of so-called “Russian mosaic” was very popular. This technique of decoration was used for cladding of columns, mantels, pilasters, countertops, large floor vases, clocks and other decorative items for the palace interiors. The main feature of this technique was that the colored semi-precious stone (malachite or lapis lazuli, rhodonite or agate, and other stones with a beautiful pattern) sawed into sheets of some millimeters thick. The base of the product made of another, usually less expensive stone was covered with these sheets. All sheets of decorative stone were carefully chosen by color and pattern.
Thus, visually the product seemed to be made of a single piece of the same malachite. Unlike Florentine mosaic technique, for example, “Russian mosaic” was good not only for flat surfaces, but also for figure (products of cylindrical, spherical, and other) forms. The weight of decorative stone sheets was fitted carefully to make the seams completely invisible. All sheets being pasted, this faced surface was ground and polished in a special way. For example, fine-grained sandstone and so-called “English Stone” (it was special thin shale), but not sandpaper was used for the surface treatment of malachite. Overburnt and finely comminuted bone, and then – powder of tin overburnt together with strong vodka with the addition of sulfur was used for polishing of malachite. Note that modern method of “Russian mosaic” implies the use of polyether mastics to glue decorative sheets. But this method has a significant drawback: eventually porous stone turns yellow and loses its decorative qualities. And if the fragments were fitted to each other not accurately, the resulting gaps are filled with the same mastics mixed with malachite crumbs. If at this stage the work was done carelessly, then the appearance of the product will eventually show more serious defects than just yellowing. Skilled craftsmen of “Russian Mosaic” have historically used different composition – it was a wax-rosin basis. This mixture allowed easily to perform seamless transitions, but also to neutralize the possibility of errors. For example, if some decorative element was damaged, this basis can be easily heated up and one can take out all the details without violating transitions. Thus, all errors were very accurately corrected directly in the process. A striking example of “Russian Mosaic” and in general the use of malachite for decorative interior items is the Malachite Room in the Hermitage. Besides the fact that the room is full of unique items made of this stone, the whole composition is arranged in such a way that it seems like a huge hall, and everything you see in it are completely carved of a single block of stone.
Deposits of malachite
Malachite of a very high quality is mined in the Urals, in the copper deposits of Nizhny Tagil, in the Burro Burro (South Australia), Katanga. Malachite occurs in the copper ores of Cornwall, France, Cuba, Chile and the USA (Arizona). Also, this stone is mined in Zimbabwe, Romania, Namibia and Zaire. One of the main sources of malachite used for making jewelry is the deposit in the Congo.