Where is Moonstone with Black Tourmaline found?
Orthoclase Feldspar with Schorl
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Open the appMoonstone with Black 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 Moonstone with Black Tourmaline
Sri Lanka
Known for high-quality moonstone, often found in alluvial deposits and pegmatites. Black tourmaline is also present in many Sri Lankan pegmatites.
India
Significant source of moonstone, particularly from the Odisha region. Tourmaline is also widely distributed in Indian pegmatites.
Madagascar
Produces various feldspar varieties and tourmaline, including occurrences where they are found together in pegmatitic intrusions.
Brazil
Famous for its pegmatite deposits, which yield both feldspars and tourmalines, making co-occurrences possible.
Myanmar (Burma)
Historically a source of fine moonstone, and tourmaline is also found in the region's gem-bearing pegmatites.
Collecting tips
- Geological Context. Focus on areas known for granitic pegmatites, which are the primary geological environment for the co-crystallization of orthoclase feldspar (moonstone) and schorl (black tourmaline).
- Visual Identification. Look for the characteristic adularescence of moonstone (a floating bluish-white sheen) combined with the opaque, black, often prismatic crystals of tourmaline. The contrast is usually quite evident.
- Hardness Test. Moonstone (Orthoclase) has a Mohs hardness of 6-6.5, while Black Tourmaline (Schorl) has a hardness of 7-7.5. This difference can be subtle but might be noticeable with careful testing on separate components if large enough.
- Cleavage vs. Fracture. Observe the cleavage of the moonstone component (two directions at nearly 90 degrees) and the conchoidal to uneven fracture of the tourmaline, which lacks distinct cleavage.
Quick Check
- Color:
- White, grey, pale blue with adularescence (moonstone) and opaque black (tourmaline).
- Luster:
- Vitreous to pearly (moonstone) and vitreous to resinous (tourmaline).
- Streak:
- White (moonstone) and white (tourmaline).
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