Thulite

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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
ColorPink
Crystal habit Massive
Cleavage Perfect {010} imperfect {100}
Fracture Uneven to conchoidal
Mohs scale hardness6.5
Luster Vitreous, pearly on cleavage surfaces
Streak White or colorless
Specific gravity 3.10–3.38
Optical propertiesbiaxial 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 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 throughout 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.[ citation needed ]

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3
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Vesuvianite, also known as idocrase, is a green, brown, yellow, or blue silicate mineral. Vesuvianite occurs as tetragonal crystals in skarn deposits and limestones that have been subjected to contact metamorphism. It was first discovered within included blocks or adjacent to lavas on Mount Vesuvius, hence its name. Attractive-looking crystals are sometimes cut as gemstones. Localities which have yielded fine crystallized specimens include Mount Vesuvius and the Ala Valley near Turin, Piedmont.

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<span class="mw-page-title-main">Sauland</span> Village in Hjartdal, Norway

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Manganoan calcite or manganocalcite is a variety of calcite rich in manganese, which gives the mineral a pink color. Its chemical formula is (Ca,Mn)CO3. It was first reported from the Banská Štiavnica Mining District, Slovak Republic, but is widely distributed around the world, notably in the Cave of Swords at Naica, Chihuahua, Mexico as well as in Bulgaria.

<span class="mw-page-title-main">Serandite</span> Mineral

Serandite is a mineral with formula Na(Mn2+,Ca)2Si3O8(OH). The mineral was discovered in Guinea in 1931 and named for J. M. Sérand. Serandite is generally red, brown, black or colorless. The correct name lacks an accent.

<span class="mw-page-title-main">Caryopilite</span> Phyllosilicate mineral

Caryopilite (synonymous with ectropite and ektropite) is a brown-colored mineral with formula (Mn2+,Mg)3Si2O5(OH)4. The mineral was discovered in 1889 from a mine in Sweden. It was named for the Greek words for walnut and felt in reference to its appearance.

Manganopyhllite is a manganese-rich variety of biotite. It was first discovered in the Harstigen mine in Sweden. The mineral was first described in 1890. The earliest use is from Edward Dana.

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.