Where is Green Onyx found?
Calcite (variety of banded calcite or travertine)
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Open the appGreen Onyx 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 Green Onyx
Mexico
Known for significant deposits, particularly in the state of Puebla, producing high-quality Green Onyx often referred to as 'Mexican Onyx'.
Pakistan
A major source of Green Onyx, particularly from the Balochistan province, known for its vibrant green varieties.
Iran
Historically and currently a significant producer of various onyx marbles, including green varieties.
Turkey
Known for travertine and onyx marble deposits, some of which exhibit green coloration.
Egypt
Ancient quarries in Egypt yielded 'Oriental Alabaster' which included banded calcite, some with green hues.
USA
Limited deposits of banded calcite (travertine/onyx marble) can be found in states like Arizona, California, and Utah, though green varieties are less common than in other regions.
Collecting tips
- Geological Context. Look for Green Onyx in areas with limestone bedrock, particularly near caves, hot springs, or ancient spring deposits. These are environments conducive to calcite precipitation.
- Visual Identification. Identify by its characteristic green color, often with parallel banding of varying shades of green, white, or cream. Its translucency is a key feature.
- Hardness Test. Perform a scratch test. Calcite has a Mohs hardness of 3, meaning it can be easily scratched by a copper coin (hardness ~3.5) or a steel knife (hardness ~5.5). This distinguishes it from true onyx (quartz, hardness 7).
- Acid Test (Caution Recommended). A small drop of dilute hydrochloric acid (HCl) will cause calcite to effervesce (fizz) due to the release of carbon dioxide. This is a definitive test for calcite but should be done carefully on an inconspicuous area as it can damage polished surfaces.
- Specific Gravity. While not a field test, its specific gravity (2.71 g/cm³) can help differentiate it from other minerals if laboratory equipment is available.
Quick Check
- Color:
- Green, often banded with white/cream
- Luster:
- Vitreous to waxy
- Streak:
- White
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