Thulite

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Thulite
Thulite.jpg
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 (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 jewellery 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]

References[edit]

  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. ^ a b c Mindat with location data