Ruby in Zoisite
Zoisite with Corundum variety Ruby (Anyolite) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Orthorhombic (Zoisite) and Trigonal (Ruby); specimen shown is a polished massive aggregate.
Mineral Group
Silicates (Sorosilicate) and Oxides (Corundum group)
Chemical Formula
(Ca2Al3(SiO4)3(OH)) + (Al2O3:Cr)
Formation Process
Metamorphic; typically forms in regional metamorphic rocks such as amphibolite or eclogite where magnesium-rich rocks undergo high-pressure transformation.
About This Crystal
An opaque, massive rock consisting of a vibrant green Zoisite groundmass interspersed with purplish-red Ruby crystals. It features a vitreous to dull luster and occasionally contains black streaks of Tschermakite (hornblende).
Physical Characteristics
Color: Green and Pink/Red; Streak: White; Cleavage: Perfect on {010} for zoisite; Fracture: Uneven to conchoidal; Specific Gravity: 3.35-3.38; Fluorescence: Ruby inclusions may glow bright red under longwave UV.
Optical Properties
Opaque aggregate; Zoisite has a refractive index of 1.69-1.70; Ruby has an RI of 1.76-1.77. No transparency means common optical phenomena like fire are not visible.
Hardness & Durability
Origin Region
Mundarara Mine, Longido District, Tanzania
Hardness & Durability
Mohs 6 to 6.5 (Zoisite) with Ruby inclusions at 9.0. Toughness is generally good, but the varying hardness between minerals can make polishing difficult.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaners as they may cause fractures along the mineral boundaries. Store away from harder gemstones like diamonds.
Rarity & Value
Relatively common but found mostly in Tanzania. Value is based on the balance of green Zoisite and red Ruby; bright red 'puddles' increase value. Frequent as beads, carvings, and tumbled stones.
Special Characteristics
Strong UV fluorescence in the red areas due to Chromium content in the Rubies. The contrast between the green and red is the primary diagnostic feature.
Lore & History
Discovered in 1954 in Tanzania. Traditionally known as 'Anyolite' (from the Maasai word for green). It is historically associated with vitality, the heart chakra, and balancing individuality with connection to others.