Orthoamphiboles with pronounced iridescence are found in eight localities in the vicinity of Nuuk, the capital of Greenland. The iridescence, difficult to see on rough samples, becomes clearly visible when the material is cut. This iridescent orthoamphibole is mined by a company wholly owned by Nuuk commune, and is sold under the trade name Nuummite. This orthoamphibole has a composition similar to that of iridescent orthoamphiboles described earlier from Greenland as well as from New Hampshire and Massachusetts, but is believed to be the first such orthoamphibole to be regarded as a gemstone.
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