Where is Feldspar found?
KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8
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Open the appFeldspar 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 Feldspar
Norway
Known for large deposits of various feldspar types, including amazonite (a green microcline variety).
United States
Significant deposits in North Carolina, South Dakota, and California, particularly for industrial uses.
Canada
Producers of industrial feldspar, especially in Quebec and Ontario.
Russia
Extensive occurrences of various feldspar minerals across the vast landmass.
Brazil
Source of some gem-quality feldspars and industrial varieties.
Collecting tips
- Igneous Rocks. Look for feldspar crystals in granites, syenites, and pegmatites. Pegmatites often host very large, well-formed feldspar crystals.
- Metamorphic Rocks. Examine gneisses and schists, where feldspar is a common constituent, often appearing as lighter-colored bands or porphyroblasts.
- Sedimentary Rocks. In arkosic sandstones, feldspar grains will be visible, often appearing angular and less weathered than quartz.
- Cleavage. Utilize the characteristic two cleavage planes at or near 90 degrees as a primary identification feature. Plagioclase often shows fine parallel striations on one cleavage face.
- Hardness Test. Feldspar has a Mohs hardness of 6 to 6.5, meaning it can scratch glass but will be scratched by quartz.
Quick Check
- Color:
- White, gray, pink, red, green, brown (variable)
- Luster:
- Vitreous to pearly
- Streak:
- White
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