Thulite
Zoisite var. Thulite · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Orthorhombic; typically massive, compact, or columnar habit without well-formed distinct crystals in this variety
Mineral Group
Silicates; Subgroup Sorosilicates
Chemical Formula
Ca2Al3(SiO4)(Si2O7)O(OH)
Formation Process
Metamorphic formation, specifically in hydrothermal veins and contact metamorphic zones associated with granitic pegmatites and calcium-rich rocks
About This Crystal
The specimen features a pale greyish-green to off-white matrix interspersed with distinct patches of vibrant pink to rose-red coloration. It is opaque with a sub-vitreous to greasy luster, showing a massive and compact structure characteristic of thulite aggregates.
Physical Characteristics
Color is pale green and white with rose-pink patches; streak is white; cleavage is perfect in one direction; fracture is uneven to sub-conchoidal; specific gravity is around 3.10 to 3.38; tenacity is brittle
Optical Properties
Biaxial positive with a refractive index ranging from 1.691 to 1.702; birefringence is 0.010 to 0.015; pleochroism is distinct in shades of pink, yellow-pink, and colorless
Hardness & Durability
Origin Region
Telemark, Norway; also found in Western Australia, Austria, Italy, and North Carolina, USA; typically forms in metamorphic environments
Hardness & Durability
Mohs hardness of 6 to 6.5; toughness is fair to good, but perfect cleavage requires care to avoid breakage; suitable for cabochons and carvings rather than high-impact rings
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid ultrasonic cleaners and steam cleaning; protect from harsh acids and sudden temperature shocks
Rarity & Value
Uncommon to Rare; value depends on the intensity and distribution of the pink color against the matrix; generally affordable as mineral specimens or cabochons, with exceptional material fetching higher collector prices; untreated
Special Characteristics
Characterized by its distinct manganese-caused pink color embedded within a zoisite matrix, creating striking color contrast patterns
Lore & History
Named after Thule, an ancient northern geographical location often associated with Scandinavia; discovered in Norway in 1820 where it was later named the national mineral of Norway; in crystal healing, it is associated with the heart chakra, vitality, and emotional healing, though these are traditional beliefs and not scientific claims