Where is Tourmaline found?
Complex borosilicate mineral group
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Open the appTourmaline 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
Brazil
Minas Gerais is a world-renowned source for gem-quality tourmaline, including rubellite, indicolite, and watermelon tourmaline, primarily from pegmatite deposits.
United States
Maine and California (especially San Diego County) are historically significant for gem tourmaline, particularly pink and green varieties from pegmatites.
Afghanistan
Known for fine quality rubellite and indicolite, often found in pegmatite deposits in the Nuristan and Kunar provinces.
Pakistan
Produces excellent gem-quality tourmaline, including pink, green, and bi-color varieties, from pegmatites in the Gilgit-Baltistan region.
Africa (e.g., Nigeria, Mozambique, Madagascar)
Various African countries are significant producers of gem tourmaline, including Paraíba-type tourmaline (copper-bearing elbaite) from Mozambique and Nigeria, and a wide range of colors from Madagascar.
Russia
The Ural Mountains are known for schorl and some gem-quality tourmaline.
Collecting tips
- Look for Pegmatites. Tourmaline is most commonly found in granitic pegmatites. Look for coarse-grained igneous rocks with large crystals of quartz, feldspar, and mica, as these are prime environments for tourmaline.
- Identify Triangular Cross-Sections. A key identifying feature of tourmaline is its characteristic rounded triangular cross-section when broken or viewed perpendicular to the crystal length. This helps distinguish it from amphiboles.
- Check for Striations. Many tourmaline crystals exhibit prominent vertical striations (parallel lines) on their prism faces. This is a good indicator.
- Observe Color and Pleochroism. While color is highly variable, the presence of strong pleochroism (different colors when viewed from different angles) is a diagnostic feature for many gem-quality tourmalines.
- Examine Metamorphic Rocks. In metamorphic terrains, search for tourmaline in schists, gneisses, and quartzites, especially those associated with boron-rich protoliths or hydrothermal alteration.
Quick Check
- Color:
- Highly variable (black, pink, red, green, blue, brown, yellow, colorless, multi-colored)
- Luster:
- Vitreous to resinous
- Streak:
- White
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