Thulite
Thulite from Leksvik, Norway.
General
CategorySorosilicate variety
Formula
(repeating unit)		(Ca,Mn)2Al3(SiO4)(Si2O7)O(OH)
Crystal systemOrthorhombic
Identification
ColorPink
Crystal habitMassive
CleavagePerfect {010} imperfect {100}
FractureUneven to conchoidal
Mohs scale hardness6.5
LusterVitreous, pearly on cleavage surfaces
StreakWhite or colorless
Specific gravity3.10–3.38
Optical propertiesbiaxial positive
Refractive index1.69–1.70
Birefringence0.006–0.018
PleochroismPresent, dichroism or trichroism depending on color.

Thulite (sometimes called rosaline) is a translucent, crystalline or massive pink manganese-bearing variety of the mineral zoisite. Manganese substitutes for calcium in the structure with up to two percent Mn2+.[1] Thulite is often mottled with white calcite and occurs as veins and fracture fillings transecting many types of rock. In mineralogical literature, thulite may sometimes refer to any pink zoisite. Clinothulite is the manganese bearing variety of monoclinic clinozoisite.[2]

Thulite was first discovered at a place called Sauland in Telemark, Norway in 1820.[3] It is named after the mythical island of Thule in the belief that the island is Scandinavia.[3] Thulite is used as a gemstone and carving material in the manufacture of jewelry and ornamental objects.

Thulite is also found in the Austrian Tyrol and in Mitchell County, North Carolina. A new, more recent find of a small quantity of thulite was discovered near Riverside in Okanogan County, Washington, US[3] and in Snillfjord i Trøndelag, Norway during tunnel constructions in December 2018.[4] Thulite is also found in New Zealand in the Otago region of the South Island.

Thulite is also found in Namibia. The occurrence is spread through out the Namib Desert and generally has ridges with a NE to SW setting. The color can be highly variable with most deposits being greenish in nature, but on occasion the desirable pink color is to be found.

References

  1. ↑ Deer, Howie and Zussman, An Introduction to the Rock Forming Minerals, Longman, 1966, p. 62, ISBN 0-582-44210-9
  2. ↑ http://www.mindat.org/min-27132.html Mindat - Clinothulite
  3. 1 2 3 Mindat with location data
  4. ↑ "Uventet funn av rosa stein får hobbygeologer til å juble". 9 December 2018.
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