What is Anyolite?
Anyolite, also known as ruby in zoisite, is a striking and colorful metamorphic rock composed primarily of green zoisite, black hornblende, and vivid red ruby crystals.
The name “anyolite” is derived from the Masai word “anyoli,” meaning “green,” referencing the dominant green hue of the zoisite matrix. This gemstone has been popular in lapidary arts for its eye-catching color contrast and is often used in carvings, cabochons, and ornamental jewelry.
The combination of ruby and zoisite makes anyolite a unique stone both for its aesthetics and mineralogical composition.
Physical Properties of Anyolite
Anyolite stands out due to its multicolored appearance—typically featuring patches of green zoisite, red ruby crystals, and streaks or veins of black hornblende. The juxtaposition of bright ruby against the rich green zoisite makes anyolite an appealing and visually dynamic gemstone. The ruby, being the most valuable component, adds a strong contrast that enhances the overall appearance of the stone.
Physical Characteristics:
- Chemical Classification: Mixed rock containing ruby (corundum), zoisite, and hornblende
- Color: Green (zoisite), red (ruby), black (hornblende)
- Streak: White
- Luster: Vitreous to pearly (zoisite), vitreous (ruby), and submetallic (hornblende)
- Diaphaneity: Opaque, with occasional translucent ruby crystals
- Cleavage: Zoisite has perfect cleavage in one direction; ruby and hornblende have none
- Mohs Hardness: 6-7 (depending on the dominance of ruby or zoisite)
- Specific Gravity: 3.3 to 3.5
- Diagnostic Properties: Vivid red ruby inclusions, green zoisite matrix, and black hornblende veins
- Chemical Composition:
- Zoisite: Ca₂Al₃(Si₂O₇)(SiO₄)O(OH)
- Ruby (Corundum): Al₂O₃
- Hornblende: Complex inosilicate series of minerals
- Crystal System: Ruby (hexagonal), zoisite (orthorhombic)
Formation and Geological Occurrence
Anyolite forms in metamorphic environments, where high pressures and temperatures cause the alteration of rocks rich in aluminum and calcium. The green zoisite matrix forms as part of the larger zoisite family of minerals, while the ruby crystals are embedded within this matrix, creating a unique combination of minerals.
Most commercially significant deposits of anyolite are found in Tanzania, specifically in the region of Longido near Mount Kilimanjaro. This is the only known area where anyolite is mined extensively, giving the stone a connection to the region’s rich geological and cultural history. The stone forms in environments where zoisite-rich schists and metamorphic rocks undergo significant pressure, allowing for the inclusion of ruby and hornblende.
Uses of Anyolite
Anyolite’s unique appearance makes it highly sought after in the lapidary arts. It is commonly used for:
- Cabochons: The stone is cut into smooth, domed cabochons to showcase its color contrast.
- Sculptures and Carvings: Anyolite’s hardness makes it suitable for carving into figurines and ornamental pieces.
- Jewelry: Though less common for rings due to its potential cleavage, anyolite is frequently used in pendants, necklaces, and brooches where the stone’s striking visual appeal can be highlighted.
- Decorative Objects: Larger pieces of anyolite are used as decorative stones or display pieces due to their unique appearance.
Gemology of Anyolite
Anyolite is a combination of ruby, zoisite, and hornblende, with ruby being the most valuable gem component. The vibrant contrast between the deep red ruby and the green zoisite is what makes anyolite so prized among gem collectors. The ruby inclusions range from small flecks to larger, well-formed crystals within the zoisite matrix.
While the ruby in anyolite can sometimes be faceted, it is more commonly left in its natural matrix form and polished as part of the stone. The zoisite component, despite having cleavage, is durable enough for most jewelry uses, though care should be taken with pieces that are frequently exposed to impacts or stress.
Identification Tips
- Color: Look for the characteristic combination of green zoisite, red ruby inclusions, and black hornblende streaks.
- Hardness: With a Mohs hardness of 6-7, anyolite can scratch glass but may still be softer than other gemstones.
- Luster: Zoisite shows a pearly luster, while the ruby inclusions have a vitreous luster, making them easy to spot.
- Crystal Form: Ruby appears as hexagonal crystals embedded within the matrix of zoisite.
Notable Locations
The Longido mining region in Tanzania is the primary and most notable source of anyolite, with smaller occurrences potentially found in other metamorphic rock deposits. The Tanzanian deposits have produced high-quality stones since their discovery in the 1950s, making them the go-to location for gem-quality anyolite.
Durability and Care
Anyolite is relatively durable with a hardness range between 6 and 7, but it requires some care to avoid chipping due to the cleavage properties of zoisite. It’s best suited for pendants, earrings, and necklaces, where it is less likely to experience impact. Clean anyolite with warm, soapy water and a soft cloth, and avoid harsh chemicals or ultrasonic cleaners that could damage the stone.
