The name of the green stone with black lines is malachite. Malachite is a copper carbonate hydroxide mineral with a chemical composition of Cu2(CO3)(OH)2. It is a popular semi-precious stone that has been used in jewelry and ornaments since ancient times. Malachite often forms botryoidal masses with distinctive green banded patterns, which makes it easily recognizable. In this article, we will explore the properties, formation, uses and history of malachite in more detail.
Physical Properties
Malachite has several distinctive physical properties:
Color: Vibrant green, often with banding patterns in lighter and darker shades of green. The green color results from the copper content.
Luster: Silky if fibrous, or vitreous to adamantine if botryoidal.
Transparency: Opaque.
Crystal System: Monoclinic. Malachite does not often form distinct crystals and is more commonly found in granular masses.
Hardness: 3.5 – 4 on the Mohs hardness scale.
Fracture: Uneven to conchoidal.
Specific Gravity: 3.6 – 4.0. This means malachite is over 3 times as dense as water.
Here is a summary of the key physical properties of malachite:
| Color | Green with banding |
| Luster | Silky to adamantine |
| Transparency | Opaque |
| Crystal System | Monoclinic |
| Hardness | 3.5 – 4 Mohs |
| Fracture | Uneven to conchoidal |
| Specific Gravity | 3.6 – 4.0 |
The vibrant green color with banding patterns is the most recognizable physical attribute of malachite. The moderate hardness, uneven fracture, and high density are also distinctive properties.
Chemical Composition
The chemical formula for malachite is Cu2(CO3)(OH)2. This formula indicates:
– Cu – Copper, which gives malachite its green color.
– CO3 – Carbonate.
– OH – Hydroxide.
Malachite contains approximately 57.48% copper oxide, 11.15% carbon dioxide, and 31.37% water by molecular weight.
Small amounts of impurities may also be present in malachite, including iron, manganese, zinc, and calcium. The vibrant green malachite owes its color entirely to its high copper content. The carbonate and hydroxide components make malachite sensitive to acids, as these anionic groups are readily dissolved.
Geologic Occurrence and Formation
Malachite mainly occurs as a secondary mineral in the oxidized zone of copper deposits. Primary copper minerals like chalcopyrite are altered to malachite by weathering processes near the earth’s surface. The typical geologic occurrence of malachite is as follows:
1. Primary copper sulfide minerals are deposited through hydrothermal or volcanic processes. Chalcopyrite is a common primary copper mineral.
2. Groundwater interacts with the copper minerals as they are exposed to weathering conditions near the earth’s surface.
3. The copper sulfides undergo alteration and are oxidized, reforming as secondary copper minerals like malachite. This process gives malachite its iconic green and banded appearance.
4. Malachite accumulates in fractures, voids, and cavities near the copper ore body. Botryoidal malachite masses are common.
Major malachite deposits have been found in the Middle Urals region of Russia, Zaire, Australia, and in Arizona, Nevada, Utah, and New Mexico in the United States. Minor deposits occur worldwide where copper mineralization has been subjected to weathering processes.
Uses of Malachite
Malachite has been prized as a gemstone and ornamental stone since ancient times. Some key uses of malachite include:
– Jewelry: Malachite is very popular for cabochons, tumbled stones, carvings, and beads. Its striking green patterns make it valuable as a semiprecious stone.
– Carvings and Ornaments: Malachite’s banded patterns are ideal for carvings, ornamental boxes, bowls, eggs, and bells. Historically it was carved into elaborate works of art.
– Pigment: Finely ground malachite produces a vibrant green pigment known as verditer. It has historically been used as an oil and watercolor paint.
– Geological Specimens: Malachite’s botryoidalhabit and distinct green banded occurrence make it a favorite mineral specimen.
– Industrial Applications: While not a major copper ore, malachite can be roasted to produce copper metal. Some malachite is also used for leather dyeing.
While not as commercially important today as a copper ore, malachite remains highly valued as a decorative stone thanks to its striking green banded patterns.
Malachite Through History
Malachite has a long history of use stretching over thousands of years:
– Ancient Egypt (4000 – 3000 BCE): The earliest known malachite mining occurred in the Sinai Peninsula and Eastern Desert. Malachite pigment was used for decorative artifacts.
– Ancient Greece (500 BCE – 300 CE): Malachite jewelry and ornaments became fashionable, along with carvings. The Greeks associated malachite with the nature goddess Aphrodite.
– Ancient Rome (500 BCE – 400 CE): Malachite was imported from Eastern deserts to Rome to be carved into ornamental works of art and jewelry.
– Middle Ages (500 – 1400 CE): The vibrant green pigment verditer, produced from malachite, was extensively used in illuminated manuscripts and paintings.
– Tsarist Russia (1700s – 1800s): Massive malachite deposits in the Ural Mountains were heavily mined to produce works of art, columns, vases, and ornaments for the Russian aristocracy. The malachite room in the Hermitage Museum is an iconic example.
– 19th Century: Malachite jewelry gained popularity after the discovery of large deposits in Australia. It was also used extensively for Victorian paperweights.
– Today: Malachite remains a popular semiprecious stone for jewelry and ornaments, with the distinctive banded pattern being highly valued.
Malachite’s long history reveals an enduring human fascination with this vividly patterned green mineral. It remains a staple of the gem and mineral world.
Frequently Asked Questions
Here are answers to some common questions about malachite:
What causes the banding in malachite?
The banding is caused by subtle changes in the mineral composition during formation, particularly the amount of copper present. Higher copper content leads to darker green bands.
Where are the main sources of malachite today?
Major deposits are located in Zaire, Namibia, Australia, and in Arizona, Nevada, Utah, and New Mexico in the United States. Secondary occurrences happen worldwide where copper deposits have been exposed to weathering.
Is malachite expensive?
Compared to many precious gemstones, malachite is relatively affordable. Small pieces suitable for tumbled stones or beads can cost as little as $5-$10 per carat. Carvings and jewelry with large banded stones will be higher valued.
How is malachite shaped and polished?
The typical process is to cut malachite into a cabochon shape, sometimes rounded. Smoothing and polishing brings out malachite’s characteristic silk-like luster and banded pattern. Delicate carvings are also polished.
What are some malachite imitations?
Green fluorite, chrysocolla, and stained agates may sometimes imitate malachite’s green banded appearance. Close inspection of properties like hardness can usually distinguish the real malachite.
Conclusion
In summary, malachite is the green banded copper carbonate mineral known for its ornamental value. Its vivid color and distinctive patterns make it uniquely suited to jewelry, carvings, and other decorative uses. Malachite has been prized since ancient Egyptian times for these beautiful attributes. While not an important copper ore, malachite remains in high demand today among mineral collectors, carvers, and jeweler designers who wish to take advantage of its one-of-a-kind appearance. The vibrant bands set against the rich green backdrop of malachite will likely continue to mesmerize us well into the future.
