Helgustadir mine
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Helgustadir mine (Icelandic: Helgustaðanáma [ˈhɛlkʏˌstaːðaˌnauːma]) is a mine in the east of Iceland where Iceland spar (a form of transparent calcite) was mined from the mid-17th century to the 20th century.[1] It is the source of the largest and clearest known Iceland spar specimen and the source of most museum specimens of Iceland spar.[2]
It was declared a nature reserve in 1975.[2]