Titanite - CaTiSiO5

Sphene is named from the greek word "sphenos" for wedge, because of its typical wedge shaped crystal habit. It is also alternatively called titanite for its titanium content.
Titanite is an orthosilicate with independent SiO4 tetrehedra united by Ti4+ in octahedral coordination and Ca2+ in sevenfold coordination.
Al3+ or Fe3+ may partially replace Ti4+ and are most common impurity.

A rather common accessory mineral in igneous rocks, being found as small crystals in granites, diorites, syenites, nephelite syenites. Also found often in crystals of considerable size embedded in the metamorphic rocks, gneiss chorite-schist and crystalline limestone. Very commonly associated with chlorite. Also found with iron ores, pyroxene, amphibole, scapolite, ziron, apatite feldspar, quartz, etc.
Titanite may alter to a fine-grained aggregate of Ti-oxides such as rutile or anatase.

Optical Properties:
Relief: High
Color: Pale brown or pale yellow
Interference colors: Strong but masked by the color of the mineral.
Cleavage: Distinct prismatic on (110)
Form: Commonly appears as diamond-shaped or wedge-shaped section.


Bibliography



• Deer, W.A., Howie, R.A., Zussman, J. (1998) Rock-forming Minerals.
• Optical Mineralogy : The Nonopaque Minerals by Phillips / Griffen
• E. WM. Heinrich (1956): Microscopic Petrografy. Mcgraw-hill book company,inc


Photo
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Titanite crystal. PPL image. 10x (Field of view = 2mm)
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Titanite crystal. XPL image. 10x (Field of view = 2mm)
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Titanite crystal. XPL image. 10x (Field of view = 2mm)
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Titanite crystals. PPL image. 10x (Field of view = 2mm)
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Titanite crystals. PPL image. 10x (Field of view = 2mm)
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Titanite crystals. XPL image. 10x (Field of view = 2mm)
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Titanite crystals. XPL image. 10x (Field of view = 2mm)
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Titanite crystals. XPL image. 10x (Field of view = 2mm)
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Titanite crystals. XPL image. 10x (Field of view = 2mm)
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Titanite crystal in a Granite. PPL image. 10x (Field of view = 2mm)
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Titanite crystal in a Granite. PPL image. 10x (Field of view = 2mm)
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Titanite crystal in a Granite. XPL image. 10x (Field of view = 2mm)
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Titanite crystal in a Granite. XPL image. 10x (Field of view = 2mm)
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Titanite crystal in a Granite. PPL image. 10x (Field of view = 2mm)
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Titanite crystal in a Granite. XPL image. 10x (Field of view = 2mm)
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Titanite crystal in a Granite. PPL image. 10x (Field of view = 2mm)
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Titanite crystal in a Granite. XPL image. 10x (Field of view = 2mm)