Where is Green Onyx found?
Banded Calcite (often marketed as Onyx Marble or Green Onyx)
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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 states of Puebla and Oaxaca, producing a wide range of colors including green.
Pakistan
A major source of green onyx, particularly from the Balochistan province, known for its vibrant green hues.
Iran
Historically a significant producer of 'onyx marble' (banded calcite), with various colorations including green.
Turkey
Contains numerous travertine and cave deposits that yield banded calcite suitable for ornamental use.
Egypt
Ancient quarries in Egypt produced 'Egyptian alabaster,' which is a form of banded calcite, sometimes with greenish tints.
USA
Deposits can be found in various states with karst topography or hot springs, such as Arizona, California, and Utah, though commercial production of green varieties is less prominent.
Collecting tips
- Look for Karst Topography. Focus on regions with limestone bedrock, caves, and active or ancient hot springs, as these are the primary environments for banded calcite formation.
- Identify Banding. The most distinctive feature is the parallel banding. Look for layers of varying color and translucency. This differentiates it from massive, unbanded calcite.
- Perform an Acid Test (Carefully). Calcite effervesces vigorously with dilute hydrochloric acid (HCl). A small drop will produce bubbles. This is a definitive test to distinguish it from true onyx (quartz), which does not react. Always wear appropriate safety gear and use a small, inconspicuous area.
- Check Hardness. Green Onyx (calcite) has a Mohs hardness of 3, meaning it can be scratched by a copper coin or a steel knife. True onyx (quartz) has a hardness of 7 and cannot be scratched by these tools.
- Observe Translucency. Many varieties of green onyx are translucent, allowing light to pass through, especially in thinner sections. Hold a thin piece up to a light source to observe this characteristic.
Quick Check
- Color:
- Green, often banded with white, yellow, or brown.
- Luster:
- Vitreous to waxy.
- Streak:
- White.
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