Thulite

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
Thulite from Leksvik, Norway.
General
Category	Sorosilicate variety
Formula (repeating unit)	(Ca,Mn)2Al3(SiO4)(Si2O7)O(OH)
Crystal system	Orthorhombic
Identification
Color	Pink
Crystal habit	Massive
Cleavage	Perfect {010} imperfect {100}
Fracture	Uneven to conchoidal
Mohs scale hardness	6.5
Luster	Vitreous, pearly on cleavage surfaces
Streak	White or colorless
Specific gravity	3.10-3.38
Optical properties	biaxial positive
Refractive index	1.69-1.70
Birefringence	0.006-0.018
Pleochroism	Present, dichroism or trichroism depending on color.

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]

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. Mindat with location data
4. https://www.nrk.no/trondelag/stort-funn-av-det-rosa-mineralet-thulitt-far-norske-hobbygeologer-til-a-juble-1.14324283