Where is Black Tourmaline in Mica Schist found?
Schorl (Tourmaline Group) in Mica Schist
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Open the appBlack Tourmaline in Mica Schist 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 Black Tourmaline in Mica Schist
Brazil
Minas Gerais and other regions are famous for various tourmaline occurrences, including schorl in metamorphic rocks.
United States
Maine, California, and other Appalachian regions have metamorphic rocks with tourmaline.
Africa
Various countries, including Namibia and Madagascar, are known for tourmaline deposits in metamorphic and pegmatitic environments.
Europe
Alps (e.g., Switzerland, Austria), and other metamorphic belts.
Collecting tips
- Look for Metamorphic Terrains. Focus your search in regions known for regional metamorphism, especially those with pelitic (shale-derived) or psammitic (sandstone-derived) schists.
- Identify Schistosity. Recognize the characteristic foliation (schistosity) of the host rock, which is indicative of metamorphic processes.
- Search for Porphyroblasts. Look for larger, often black, prismatic crystals that stand out from the finer-grained mica matrix. These are likely schorl porphyroblasts.
- Check for Boron-Rich Environments. While not always obvious, the presence of nearby granitic intrusions or pegmatites can indicate a source of boron, which is essential for tourmaline formation.
Quick Check
- Color:
- Black crystals in a silvery/dark gray foliated matrix
- Luster:
- Vitreous to resinous (tourmaline), pearly to vitreous (mica)
- Streak:
- White (for schorl, though rarely tested in situ)
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