Where is Potassium Feldspar found?
Orthoclase
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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
Known for large, well-formed pink orthoclase crystals, often associated with smoky quartz and amazonite (microcline).
St. Gotthard Massif, Switzerland
Produces excellent examples of orthoclase crystals, sometimes twinned.
Madagascar
Source of large orthoclase crystals, including some gem-quality material.
Brazil
Various localities yield orthoclase, often in pegmatites.
Norway
Known for occurrences of orthoclase in granitic pegmatites.
Collecting tips
- Look in Granitic Rocks. Orthoclase is a primary constituent of granite and related felsic igneous rocks. Examine outcrops of these rocks for pink, white, or salmon-colored crystals with characteristic cleavage.
- Check Pegmatites. Pegmatites, which are coarse-grained igneous rocks, are excellent places to find large, well-formed orthoclase crystals, often associated with quartz and mica.
- Examine Metamorphic Terrains. High-grade metamorphic rocks like gneiss and schist can contain orthoclase. Look for it as a component of the rock fabric.
- Observe Cleavage. The most distinctive feature for identification in the field is its two cleavage planes intersecting at nearly 90 degrees. This helps distinguish it from quartz (no cleavage) and plagioclase (striations).
- Consider Color and Luster. While variable, the typical pink to salmon-orange color and vitreous luster are good initial indicators.
Quick Check
- Color:
- White, pink, salmon-orange, reddish
- Luster:
- Vitreous to pearly
- Streak:
- White
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