Where is Tourmaline Granite found?
Granite (igneous rock) with Schorl (mineral)
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Open the appTourmaline Granite 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 Tourmaline Granite
Cornwall, England
Known for its extensive Variscan granites, many of which are tourmaline-bearing, particularly in association with tin-tungsten mineralization.
Maine, USA
Numerous granitic intrusions, especially in the western and central parts of the state, contain schorl and other tourmaline varieties, often in pegmatites.
Brazil
Famous for its pegmatite fields, which often occur within or adjacent to granitic bodies, yielding various tourmaline species, including schorl in granite.
Namibia
The Erongo region and other areas are known for granitic intrusions and associated pegmatites containing significant tourmaline.
Australia
Various granitic provinces, such as those in Western Australia and New South Wales, can host tourmaline-bearing granites.
Collecting tips
- Look for Granitic Terrains. Focus on areas known for large granitic intrusions, especially those associated with orogenic belts or areas of significant crustal melting.
- Identify Black Prismatic Crystals. Scan rock outcrops for distinct black, elongated, often striated crystals embedded within a lighter-colored, coarse-grained matrix. The triangular cross-section of tourmaline is a key identifier.
- Check for Associated Minerals. Tourmaline-bearing granites are often found near pegmatites, aplites, or areas with evidence of hydrothermal alteration, which can also host other interesting minerals.
- Examine Weathered Surfaces. Weathering can sometimes make the tourmaline crystals more prominent as they are generally more resistant to weathering than some other granite minerals.
Quick Check
- Color:
- Light-colored matrix (white, gray, pink) with black prismatic crystals.
- Luster:
- Vitreous (glassy) for tourmaline and quartz, dull to vitreous for feldspar.
- Streak:
- White (for granite minerals) to colorless (for tourmaline, though it's typically too hard to streak).
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