Cotterite
Extremely rare variety of quartz
Cotterite is an extremely rare variety of quartz derived from a single horizontal vein of calcite, quartz and iron-rich mudstone cut through the Carboniferous Limestone in Rockforest, County Cork in Ireland.
Cotterite crystals grow in extremely thin layers that develop very thin cracks as they grow, causing light to be scattered in a frosting effect. This gives cotterite a distinctive pearlescent finish.
It was first discovered in 1874 by Grace Elizabeth Cotter of Mallow, who presented it to the National Museum of Ireland in 1876. Robert Harkness introduced it to the Mineralogical Society of Great Britain and Ireland, naming it cotterite in honour of Cotter. Since then only about 30 specimens have ever been found.
In 2024, a young boy named Ben O’Driscoll discovered a piece of cotterite in a newly ploughed field in Rockforest. This was the first time a specimen of cotterite had been found in 150 years.
Sources and credits
This article is adapted from the Wikipedia article “Cotterite”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- Cotterite - The World’s Rarest form of Quartz.jpg by National Museum of Ireland, CC BY-SA 2.0
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