Where is Corundum found?
Al2O3
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Open the appCorundum 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 Corundum
Myanmar (Burma)
Famous for high-quality rubies, particularly from the Mogok Stone Tract.
Sri Lanka
A historic source of a wide variety of sapphires and rubies, often found in placer deposits.
Thailand
Known for rubies and sapphires, particularly from the Chanthaburi and Trat provinces.
Cambodia
Produces rubies and sapphires, often associated with basaltic rocks.
Madagascar
A significant source of various colored sapphires and rubies, discovered in numerous localities.
Australia
Eastern Australia (New South Wales, Queensland) is a major producer of blue and fancy-colored sapphires from alluvial deposits.
United States
Localities in Montana (Yogo Gulch for blue sapphires, Rock Creek for various colors) and North Carolina (emery and some gem-quality corundum).
Kashmir (India/Pakistan)
Historically renowned for highly prized 'cornflower blue' sapphires, though production is now limited.
Tanzania
Produces rubies (e.g., Winza, Longido) and sapphires (e.g., Tunduru, Umba Valley).
Collecting tips
- Look in Placer Deposits. Due to its high specific gravity and hardness, corundum often concentrates in alluvial (placer) deposits. Look in riverbeds, stream gravels, and ancient river terraces.
- Identify Associated Minerals. Corundum is often found with minerals like spinel, garnet, kyanite, sillimanite, feldspar, and mica in metamorphic and igneous environments. The absence of quartz is a key indicator in primary deposits.
- Check for Hexagonal Crystal Habit. Corundum typically forms distinctive hexagonal crystals, often barrel-shaped or tabular. Look for these characteristic forms.
- Test Hardness. Corundum is extremely hard (9 on Mohs scale). It will scratch almost all other common minerals, except diamond. This is a primary identification tool.
- Observe Parting. While lacking true cleavage, corundum exhibits parting. Look for flat, parallel planes of separation, especially on the basal pinacoid.
- Examine Luster. Corundum typically has an adamantine to vitreous luster, which can be quite bright and reflective.
Quick Check
- Color:
- Variable (red for ruby, blue for sapphire, other colors, or colorless)
- Luster:
- Adamantine to vitreous
- Streak:
- White
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