igneous
Smoky Quartz in Matrix (Pegmatite)
Silicon Dioxide (SiO2) with Potassium Feldspar and Biotite mica
Hardness: 7 (Quartz) to 6 (Feldspar); Color: Dark brown to black smoky quartz crystals embedded in pink/tan feldspar and black mica matrix; Luster: Vitreous to dull; Crystal structure: Hexagonal (Quartz) and Monoclinic (Feldspar).
- Hardness
- 7 (Quartz) to 6 (Feldspar)
- Luster
- Vitreous to dull
Identified More igneous →
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Physical properties
Hardness: 7 (Quartz) to 6 (Feldspar); Color: Dark brown to black smoky quartz crystals embedded in pink/tan feldspar and black mica matrix; Luster: Vitreous to dull; Crystal structure: Hexagonal (Quartz) and Monoclinic (Feldspar).
Formation & geological history
Formed from the slow cooling of magma in a granitic pegmatite vein, where large crystals have time to grow. The 'smoky' color in the quartz is typically caused by natural irradiation from surrounding radioactive elements in the crust, such as uranium or thorium, acting on aluminum impurities over millions of years.
Uses & applications
Used primarily for mineral collecting and lapidary work. Quartz is also used in electronics (oscillators) and glassmaking, though this specimen is aesthetic rather than industrial grade.
Geological facts
Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm'. This specific specimen shows 'graphic granite' textures, where the quartz and feldspar intergrow in patterns that resemble ancient cuneiform or hieroglyphic writing.
Field identification & locations
Identify in the field by looking for large, interlocking crystals of different colors (pink, black, clear/gray). It is commonly found in mountainous regions with exposed granitic basements, such as the Colorado Rockies, New Hampshire, or Brazil. Tip: The quartz will scratch glass, while the pink feldspar will not easily do so.
