igneous
Feldspar-Quartz Rock (likely Pegmatite or Granite)
Feldspar-Quartz composite rock (KAlSi3O8 - SiO2)
Hardness: 6-7 Mohs; Color: Pink, white, and tan; Luster: Vitreous to dull; Crystal structure: Monoclinic/Hexagonal; Cleavage: Two directions at 90 degrees (for feldspar portion).
- Hardness
- 6-7 Mohs
- Color
- Pink, white, and tan
- Luster
- Vitreous to dull
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Pink, white, and tan; Luster: Vitreous to dull; Crystal structure: Monoclinic/Hexagonal; Cleavage: Two directions at 90 degrees (for feldspar portion).
Formation & geological history
Formed from the slow cooling of magmatic fluids rich in silica and alkali metals, often in plutonic environments deep below the earth's surface.
Uses & applications
Large crystals are used in ceramics and glassmaking. As a decorative stone, it is used in countertops, landscaping, and lapidary art.
Geological facts
Feldspar is the most abundant mineral group in the Earth's crust. This specimen appears to be a coarse-grained igneous rock where individual mineral grains are easily visible to the naked eye.
Field identification & locations
Identify in the field by looking for blocky crystals with flat cleavage faces (feldspar) mixed with translucent, irregularly shaped grains (quartz). Found globally in continental crust.
