Cassiterite - SnO2

The name cassiterite is derived from the term Cassiterides which was applied for "islands off the western coast of Europe" in pre-Roman times. Cassiterite is a tin oxide mineral and it is the most important source of tin, and most of the world’s supply of tin is obtained by mining cassiterite. Small amounts of primary cassiterite are found in igneous and metamorphic rocks throughout the world. It is also a residual mineral found in soils and sediments. Cassiterite is more resistant to weathering than many other minerals, and that causes it to be concentrated in stream and shoreline sediments. Although cassiterite is the most important ore of tin, it has only been found in minable concentrations in a few locations. Cassiterite can be found in hydrothermal veins and pegmatites associated with granite intrusions. May also precipitate from volcanic gas, as shown by experiments of Africano et al. (2002), in which it deposits in the 550-240°C range.

Optical Properties:
• Form: Usually as fibrous, botryoidal crusts or concretionary masses. Granular, coarse to fine.
• Twinning: Both contact and penetration twins.
• Colour: Black, yellow, brown, red or white.
• Relief: Very High.
• Interference colours: Very High.


Bibliography



• Bucher, K., & Grapes, R. (2011). Petrogenesis of metamorphic rocks. Springer Science & Business Media.
• Fossen, H. (2016). Structural geology. Cambridge University Press.
• Howie, R. A., Zussman, J., & Deer, W. (1992). An introduction to the rock-forming minerals (p. 696). Longman.
• Passchier, Cees W., Trouw, Rudolph A. J: Microtectonics (2005).
• Philpotts, A., & Ague, J. (2009). Principles of igneous and metamorphic petrology. Cambridge University Press.
• 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.
• Vernon, R. H. (2018). A practical guide to rock microstructure. Cambridge university press.


Photo
cassiterite(1).jpg

Zoned cassiterite crystal (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)		 cassiterite(2).jpg

Zoned cassiterite crystal and tourmaline crystals. St. Just mine, Cornwall. XPL image, 2x (Field of view = 7mm)		 cassiterite(3).jpg

Zoned cassiterite crystals (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)
cassiterite(4).jpg

Zoned cassiterite crystals (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)		 cassiterite(5).jpg

Zoned cassiterite crystals and tourmaline crystals. St. Just mine, Cornwall. XPL image, 2x (Field of view = 7mm)		 cassiterite(6).jpg

Zoned cassiterite crystal (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)
cassiterite(8).jpg

Zoned cassiterite crystal (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)		 cassiterite(9).jpg

Zoned cassiterite crystal and tourmaline crystals. St. Just mine, Cornwall. XPL image, 2x (Field of view = 7mm)		 cassiterite(10).jpg

Zoned cassiterite crystal (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)
cassiterite(12).jpg

Zoned cassiterite crystal (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 10x (Field of view = 2mm)		 cassiterite(13).jpg

Zoned cassiterite crystal (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 10x (Field of view = 2mm)		 cassiterite(15).jpg

Zoned cassiterite crystal (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 10x (Field of view = 2mm)
cassiterite(21).jpg

Zoned cassiterite crystal (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 10x (Field of view = 2mm)		 cassiterite(16).jpg

Zoned, and twinned, cassiterite crystal (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 10x (Field of view = 2mm)		 cassiterite(17).jpg

Zoned, and twinned, cassiterite crystal and tourmaline crystals. St. Just mine, Cornwall. XPL image, 10x (Field of view = 2mm)
cassiterite(24).jpg

Granular cassiterite (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)		 cassiterite(26).jpg

Granular cassiterite (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)		 cassiterite(28).jpg

Granular cassiterite (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)
cassiterite(29).jpg

Granular cassiterite and tourmaline crystals. St. Just mine, Cornwall. XPL image, 2x (Field of view = 7mm)		 cassiterite(30).jpg

Granular cassiterite (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)		 cassiterite(31).jpg

Granular cassiterite (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)
cassiterite(32).jpg

Granular cassiterite (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)		 cassiterite(33).jpg

Granular cassiterite (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)		 cassiterite(34).jpg

Granular cassiterite (brown) and blue tourmaline crystals. St. Just mine, Cornwall. PPL image, 2x (Field of view = 7mm)