Malachite is a beautiful decorative stone. Its rich, patterned coloration in shades of green is unique among gems. Malachite's relative softness makes it easy to work. Despite its low hardness, it also takes a polish very well. These qualities, combined with ready availability, make malachite a popular choice for lapidary artistry. This stone is used extensively to make cabochons, beads, boxes, inlays, and carvings of all kinds. With great care, malachite can also be turned on a lathe to make goblets and candlesticks. Facetable crystals would be microscopic in size, since larger crystals are too opaque to let light through. A faceted malachite gem larger than ½ carat would be opaque. (Fibrous aggregates are packed masses of crystals. These also take a high polish).
Malachite is abundant in its typical forms, so even the best specimens are modestly priced. Pieces showing an unusual crystal habit, distinctive pattern, or chatoyancy will have higher values. Rocks consisting of malachite and other colorful copper minerals in lovely combinations generally command higher prices than pure malachites. The value of carvings and ornamental objects hinges primarily on the size and artistry of the work.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Crystallography||Monoclinic. Crystals are prismatic, usually small; also massive, sometimes banded; stalactitic; as crusts.|
|Refractive Index||1.85 (average)|
|Colors||Green (various shades due to admixed clay in massive material), dark green|
|Luster||Adamantine in crystals; vitreous; fibrous; dull.|
|Fracture||Uneven, fibrous, sub-conchoidal|
|Density||4.05 (as low as 3.6 in admixtures or when fibrous.).|
|Cleavage||Perfect 1 direction. Fracture uneven. Brittle.|
|Heat Sensitivity||Very sensitive|
|Transparency||Translucent to opaque|
|Optics||a=1.655; β=1.875; γ=1.909. Biaxial (-), 2V=43°. Mean index reading of 1.85 on massive material.|
|Etymology||From the Ancient Greek malache for mallow (an herb plant), in allusion to its color, or malakos, meaning "soft."|
|Occurrence||In the oxidized portions of copper ore bodies, with azurite and cuprite. Nodules, cone shapes, stalactitic, crusts.|
This vivid green gem gets its color from copper. Malachite is invariably associated with copper ore deposits. It’s considered one of the minor copper ores, with 58% copper content. Its recovery is generally done, at least on the large scale, as a sidelight of copper mining.
Technically, malachite is a “secondary mineral,” which means it’s created by a chemical reaction between minerals that have already formed, rather than by a simple one-step process. Malachite may form when water containing carbon dioxide or dissolved carbonate minerals interacts with preexisting copper-containing rocks or when solutions containing dissolved copper minerals interact with carbonate rocks. Malachite’s characteristic swirling and concentric patterns are a result of this formation process. These bands reflect the waxing and waning of the solutions necessary for formation and the changes in their chemical content. Most commonly, the stone occurs in massive form as a microcrystalline aggregate, in lumps, or as crust on other rocks.
Malachite may have been mined in Egypt as early as 4,000 BCE. Not only was it used as a gemstone and ornamental material, the stone was ground into pigments for painting and cosmetics. Not until the Industrial Revolution were synthetic pigments created that could rival its color. Restoration experts still use malachite pigment formulas for authenticity when conserving old paintings. Unfortunately, this beauty can also be hazardous. The copper content of the dust released from grinding malachite makes it toxic to breathe. (Today, workers involved in the mining and fashioning of the stone are advised to wear protective respiratory gear. Keeping the rough wet also keeps dust to a minimum).
Malachite has been prized by many cultures throughout history. The green stone has been used in protective amulets since ancient times. Perhaps its greatest appreciators were the Russian royals of the 19th century. They had dining sets, huge sculptures, vases, and even paneling made from it. You can take a virtual tour of the celebrated “Malachite Room” in the Winter Palace at the Hermitage Museum in St. Petersburg, Russia. The Victorians were great admirers of opaque jewelry stones. Malachite was one of their favorites. The stone was often used in small carvings, beads, and cabochons set in silver and occasionally gold.
Malachite continues to appeal to the gem lover as well as anyone interested in nature’s wonders. Mineral and gemstone collectors compete to acquire prime specimens in some of the stone’s rarer habits. Some of the most desired forms are: botryoidal masses, stalactites or slices cut from them, and pieces with splayed-out clusters of needle-like (acicular) crystals showing a velvety chatoyancy. Malachites are sometimes discovered combined with other copper-containing minerals. Blue-green chrysocolla, dark-blue azurite, or brick-red cuprite can create rocks of unsurpassed beauty when combined with malachite’s forest green.
Although synthetic malachite has been manufactured for research purposes, it’s not found commercially. The synthetic material is far more costly than the natural, abundant mineral.
Malachite is rarely enhanced. Lower quality, less compact pieces may be stabilized with plastic resins or given a surface polish with wax.
The majority of malachite rough comes from the Democratic Republic of The Congo (formerly Zaire), Namibia, Russia and the American Southwest.
- Australia: N.S.W., Broken Hill
- Democratic Republic of The Congo: banded material, also stalactitic, most familiar on marketplace.
- Namibia: Tsumeb, magnificent large crystals.
- Russia: Mednorudyansk, immense masses, some up to 50 tons! Much good for cutting. Also from mine at Nizhne-Tagilsk.
- United States: Arizona, at Bisbee and Gila, other localities; New Mexico; Tennessee; Utah.
Cabochons and carvings from banded material can be virtually any size. Stalactites have been found several feet long. Slabs have been used as paneling in palaces. Facetable crystals are virtually nonexistent. Any cut gem would be very small, less than 2 carats. Massive aggregates can weigh tons.
Malachite is soft, somewhat brittle, and sensitive to both heat and acids. It requires gentle care. Mechanical cleaning methods, such as ultrasonic or steam cleaning, are not recommended. Use in rings, bracelets, or other jewelry that may receive rough treatment or constant wear is not advisable. Use in earrings, brooches, pendants, and tie pins should pose no special problems. Consult our Gemstone Care Guide for recommended cleaning methods.
by Dr. Joel Arem; Barbara Smigel, PhD GG