Where is Feldspar with Tourmaline found?
Feldspar (KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8) with Tourmaline (Na(Mg,Fe,Li,Mn,Al)3Al6(BO3)3Si6O18(OH)4)
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Open the appFeldspar with Tourmaline 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 with Tourmaline
Brazil
Minas Gerais is famous for its pegmatites yielding gem-quality tourmaline in association with feldspar.
United States
Maine and California (especially San Diego County) are known for pegmatites with excellent tourmaline and feldspar specimens.
Afghanistan and Pakistan
Himalayan pegmatite belts produce fine tourmaline crystals often found with feldspar.
Madagascar
Numerous pegmatite occurrences with diverse tourmaline varieties and feldspar.
Collecting tips
- Look for Pegmatites. The most common and often spectacular occurrences of feldspar with tourmaline are in granitic pegmatites. These are coarse-grained igneous rocks, often found as dikes or sills cutting through other igneous or metamorphic rocks.
- Identify Characteristic Crystal Forms. Search for the distinctive prismatic crystals of tourmaline, often black (schorl), embedded in or alongside the lighter-colored feldspar. Tourmaline's triangular cross-section and striations are key identifiers.
- Check for Hydrothermal Alteration. In some cases, tourmaline can form in hydrothermal veins, so look for areas with evidence of fluid alteration within granitic or metamorphic terrains.
Quick Check
- Color:
- Feldspar: White, pink, grey. Tourmaline: Black, green, pink, blue.
- Luster:
- Vitreous to pearly (feldspar), Vitreous to resinous (tourmaline).
- Streak:
- White (feldspar), White (tourmaline, though often not easily obtained due to hardness).
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