Malachite

Malachite forms at shallow depths in the oxidizing zone above copper deposits, precipitating from descending solutions in fractures, caverns, cavities and porous rock, often in limestone; the waxing and waning of these solutions produces its bands. It occurs with azurite, cuprite, calcite and other copper minerals. Early deposits in Egypt and Israel were mined more than 4,000 years ago, and large deposits in Russia's Ural Mountains supplied much gem material in the 1800s. Most malachite on the lapidary market today comes from the Democratic Republic of the Congo, with smaller amounts from Namibia, Australia, France, Russia and Arizona.

Malachite is easy to recognise by its green colour, banding and eyes, light green streak, low hardness and high specific gravity; it is one of few green minerals that fizz in cold dilute hydrochloric acid (streak and acid tests are destructive). It is also found intergrown with azurite (azurmalachite), chrysocolla, turquoise and pseudomalachite. Treatment is uncommon, but lower-quality, porous material may be stabilised with plastic resin or waxed. Synthetic and imitation malachite has been used in jewellery; poor imitations have an unnatural colour, and better ones usually show banding and eyes without a natural geometry.

Malachite is soft, somewhat brittle and sensitive to heat and acids. Earrings, brooches and pendants pose no special problems, but rings and bracelets need protective settings. Do not use ultrasonic or steam cleaning or acidic cleaners. Wearing or displaying finished pieces is considered safe, but dust from grinding malachite is toxic to breathe because of its copper, so miners and cutters should wear respiratory protection and keep the rough wet.

The name goes back to the ancient "molochitus" (recorded by Pliny the Elder in 79 CE), from the Greek word for the mallow plant, alluding to the green of its leaves. Malachite may have been mined in Egypt as early as 4,000 BCE and was cut for jewellery and ground into pigment for painting and cosmetics; it is one of the oldest known green pigments and appears in Egyptian tomb paintings and European paintings of the 15th and 16th centuries. It has been used in protective amulets since ancient times. The Russian royals of the 19th century used it for vases, sculptures and panelling, as in the Malachite Room of the Winter Palace in St. Petersburg, and Victorian jewellers favoured it for carvings, beads and cabochons.