metamorphic
Nuummite
Nuummite (complex silicate composed of Anthophyllite and Gedrite, (Mg,Fe)7Si8O22(OH)2)
Hardness: 5.5-6.0 Mohs; Color: Black to dark brown with iridescent flashes of gold, blue, or green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good (standard for amphiboles); Specific gravity: 2.85-3.57.
- Hardness
- 5
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 5.5-6.0 Mohs; Color: Black to dark brown with iridescent flashes of gold, blue, or green; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Cleavage: Good (standard for amphiboles); Specific gravity: 2.85-3.57.
Formation & geological history
Formed through high-grade metamorphism over 3 billion years ago (Archean era). It is one of the oldest rocks on Earth, originally formed from volcanic precursors that underwent intense pressure and temperature changes.
Uses & applications
Primarily used as a gemstone for jewelry (cabochons), ornamental carvings, and by crystal collectors for its aesthetic iridescence and rare geological age.
Geological facts
Discovered near Nuuk, Greenland in 1810 by mineralogist K.L. Giesecke. The unique play of color is caused by the intergrowth of two different amphibole minerals, creating a lamellar structure that interferes with light.
Field identification & locations
Identify by its 'labradorescence-like' flashes of color against a dark/black background. It is almost exclusively found in the Nuuk region of Greenland, though similar material has been found in Mauritania and Canada. Collectors look for strong, multi-colored flashes.
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