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Thulite  (variety of Zoiste)
Current inventory:  0 gems
 

Chemistry:  Ca₂Al₃SiO₃O₁₂(OH) + Mn

Discovered in 1820;   IMA status: Valid (pre-IMA; Grandfathered).
The name Thulite is from Thule, the ancient name for Norway, where it was originally found. The name Epidote is derived from the Greek word epidosis meaning addition because the base of the crystal's prism has one side longer than the other. Zoisite is named after Siegmund Zois (1747-1819), an Austrian scientist.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/C.23-100

Nickel-Strunz 10th Ed. ID:

9.BG.10

9 : SILICATES (Germanates)
B : Sorosilicates
G : Sorosilicates with mixed SiO₄ and Si₂O₇ groups; cations in octahedral [6] and greater coordination

Related to:

Epidote Group. Zoisite is the orthorhombic dimorph of Clinozoisite and is the only orthorhombic member of the Epidote Group.

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Crystals prismatic, to 10 cm, typically deeply striated and poorly terminated; columnar to compact, massive (Thulite).

Twinning:

None

Physical Properties

Cleavage:

[001] Perfect

Fracture:

Even, Uneven, Conchoidal

Tenacity:

Brittle

Hardness (Mohs):

6.0 - 6.5

Density:

3.09 - 3.30 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Pink, deep Pink, Rose Red, Red

Transparency:

Transparent to Sub-Translucent

Luster:

Vitreous, Pearly

Refractive Index:

1.695 - 1.701  Biaxial ( + )

Birefringence:

0.0060 - 0.0180

Dispersion:

Relatively Strong; 0.019

Pleochroism:

None

Occurances

Geological Setting:

Typically in medium-grade regionally metamorphosed crystalline schists formed from igneous, sedimentary, or metamorphic rocks relatively high in calcium; in eclogites and blueschist facies metamorphic rocks.

Common Associations:

Albite, Biotite, Calcite, Garnet, Hornblende, Quartz

Type Locality:

Kleppan, Sauland, Hjartdal, Telemark, Norway

Year Discovered:

1820

View mineral photos:

Thulite Mineral Photos and Locations

More Information

Mindat.org  (Thulite)
Mindat.org  (Zoisite)
Webmineral.com  (Zoisite)

Thulite is a rare member of the Epidote Group of minerals that includes Allanite, Clinozoisite, Epidote, Hancockite, Mukhinite, Piedmontite, Tanzanite, Thulite and Zoisite. Thulite is a beautiful, deep pink, manganoan variety of Zoisite and found mainly in Norway but also found in small quantities from other locations around the world. Thulite was first discovered in Kleppan, Sauland, Hjartdal Telemark, Norway in 1820. It is often mottled with white calcite and the pink to red color is due to its manganese content. Thulite is the national gemstone of Norway and they pronounce it "too leat".
 

  
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