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Helgustadir mine on the east coast of Iceland is the world-famous source of optical grade double-refractive Calcite, known as 'Iceland Spar'. It's optical properties have been known since 1669, but official mining began in 1855 and ended in 1925. Since 1975 the site has been a national monument with collecting strictly forbidden. This lovely large miniature specimen was collected pre-1975 and has been in David Hardman's fine collection of worldwide zeolites since then. It consists of a well-formed rounded rhombic crystal of Calcite, 4.6 cm across, with natural etched faces (so no double-refraction visible), but one side it covered in perfect, cream coloured, flat, bladed Stilbite crystals. The Stilbite crystals are in great condition and reach nearly 1 cm in length. Zeolites from Helgustadir mine are now so rarely seen for sale, just the occasional quality specimen in older collections that become available.
70 x 45 x 35 mm