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.

Titanite is 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

• Cox et al. (1979): The Interpretation of Igneous Rocks, George Allen and Unwin, London.
• Howie, R. A., Zussman, J., & Deer, W. (1992). An introduction to the rock-forming minerals (p. 696). Longman.
• Le Maitre, R. W., Streckeisen, A., Zanettin, B., Le Bas, M. J., Bonin, B., Bateman, P., & Lameyre, J. (2002). Igneous rocks. A classification and glossary of terms, 2. Cambridge University Press.
• Middlemost, E. A. (1986). Magmas and magmatic rocks: an introduction to igneous petrology.
• Shelley, D. (1993). Igneous and metamorphic rocks under the microscope: classification, textures, microstructures and mineral preferred-orientations.
• Vernon, R. H. & Clarke, G. L. (2008): Principles of Metamorphic Petrology. Cambridge University Press.

Photo
Titanite crystal in an andesite from Greece. PPL image , 2x (Field of view = 7mm)	Titanite crystal in an andesite from Greece. PPL image , 2x (Field of view = 7mm)	Titanite crystal in an andesite from Greece. PPL image , 10x (Field of view = 2mm)
Titanite crystal in a haüyne foidite, Eifel, Germany. PPL image , 10x (Field of view = 2mm)	Titanite crystal in a haüyne foidite, Eifel, Germany. PPL image , 10x (Field of view = 2mm)	Titanite crystal in a rhyolite. PPL image , 10x (Field of view = 2mm)
Titanite crystal in a rhyolite. XPL image , 10x (Field of view = 2mm)	Titanite crystal in a rhyolite. XPL image , 10x (Field of view = 2mm)	Titanite crystal in a rhyolite. PPL image , 10x (Field of view = 2mm)
Titanite crystal in an andesite from Lemnos (Greece). PPL image , 2x (Field of view = 7mm)	Titanite crystal in an andesite from Lemnos (Greece). PPL image , 2x (Field of view = 7mm)	Titanite crystal in an andesite from Lemnos (Greece). XPL image , 2x (Field of view = 7mm)
Titanite crystal in an andesite from Lemnos (Greece). PPL image , 2x (Field of view = 7mm)	Titanite crystal in an andesite from Lemnos (Greece). PPL image , 10x (Field of view = 2mm)	Titanite crystal in an andesite from Lemnos (Greece). PPL image , 10x (Field of view = 2mm)
Titanite crystal in an andesite from Lemnos (Greece). PPL image , 2x (Field of view = 7mm)	Titanite crystal in an andesite from Lemnos (Greece). XPL image , 2x (Field of view = 7mm)	Titanite crystal in an andesite from Lemnos (Greece). PPL image , 2x (Field of view = 7mm)
Titanite crystal in an andesite from Lemnos (Greece). PPL image , 10x (Field of view = 2mm)	Titanite crystal in an andesite from Lemnos (Greece). PPL image , 10x (Field of view = 2mm)	Titanite crystal in an andesite from Lemnos (Greece). PPL image , 10x (Field of view = 2mm)
Titanite crystal in an andesite from Lemnos (Greece). PPL image , 2x (Field of view = 7mm)	Titanite crystal in an andesite from Lemnos (Greece). PPL image , 2x (Field of view = 7mm)