Where is Potassium Feldspar found?
Orthoclase or Microcline (KAlSi3O8)
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Open the appPotassium Feldspar occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Potassium Feldspar
Pikes Peak, Colorado, USA
Famous for large, well-formed pink orthoclase crystals, often associated with smoky quartz and amazonite (green microcline).
Madagascar
Known for large crystals of orthoclase and microcline, including gem-quality amazonite.
Norway
Significant occurrences of orthoclase and microcline in pegmatites, sometimes yielding large crystals.
Brazil
Various localities produce orthoclase and microcline, including some gem-quality amazonite.
Russia (Ural Mountains)
Historically important source of amazonite.
Collecting tips
- Look for Igneous Rocks. Potassium feldspar is a primary component of granites, syenites, and their volcanic equivalents (rhyolite, trachyte). Examine outcrops of these rocks for characteristic pink, white, or cream-colored crystals.
- Check Pegmatites. Pegmatites are coarse-grained igneous rocks often rich in large feldspar crystals. These are excellent places to find well-formed orthoclase or microcline.
- Examine Metamorphic Rocks. Gneisses and schists can contain significant amounts of potassium feldspar. Look for porphyroblasts (large crystals) within the metamorphic fabric.
- Hydrothermal Veins. Adularia, a low-temperature variety of orthoclase, can be found in hydrothermal veins, often associated with quartz and other vein minerals.
- Cleavage and Hardness Test. Confirm two cleavage directions at or near 90 degrees. Test hardness with a steel file (Mohs 6-6.5); it should scratch glass but not quartz.
Quick Check
- Color:
- Pink, white, cream, salmon-orange, green (amazonite)
- Luster:
- Vitreous to pearly
- Streak:
- White
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