Where is Schorl in Quartz found?
Schorl (Na(Fe2+)_3Al_6(BO_3)_3Si_6O_18(OH)_4) and Quartz (SiO_2)
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Open the appSchorl in Quartz 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 Schorl in Quartz
Brazil
Minas Gerais is a significant source, particularly for well-formed crystals in quartz.
United States
Maine, California, and Colorado have notable occurrences in pegmatite districts.
Madagascar
Known for various tourmaline varieties, including schorl in quartz.
Pakistan
Northern areas yield fine mineral specimens.
Afghanistan
Similar to Pakistan, known for pegmatite-related minerals.
Collecting tips
- Geological Context. Look for areas with granitic pegmatites, hydrothermal veins, or regions of high-grade metamorphism. Schorl in quartz is often found in the outer zones of pegmatite bodies.
- Visual Identification. Identify the characteristic black, prismatic crystals of schorl embedded in a lighter, often translucent quartz matrix. The vertical striations on schorl are a key identifier.
- Hardness Test. Schorl (7-7.5) and Quartz (7) are relatively hard minerals. They will scratch glass and most common metals. This can help differentiate them from softer black minerals.
- Density. Schorl is denser than quartz (specific gravity of schorl is 3.0-3.2, quartz is 2.65). While difficult to discern in an aggregate, a specimen with a high proportion of schorl will feel noticeably heavier than pure quartz.
Quick Check
- Color:
- Black (schorl) in colorless, white, or smoky (quartz)
- Luster:
- Vitreous to resinous (schorl), Vitreous (quartz)
- Streak:
- White (both schorl and quartz)
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