Where is Green Onyx found?
Banded Calcite (variety of Onyx Marble)
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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
Significant deposits, particularly in Puebla and Oaxaca, known for producing high-quality green onyx.
Pakistan
Balochistan province is a major source of various colored onyx marbles, including green varieties.
Iran
Historical and contemporary source of onyx marble, often referred to as 'Oriental Alabaster'.
Turkey
Known for various types of travertine and onyx marble deposits.
Egypt
Ancient source of alabaster, which often included banded calcite varieties.
USA
Deposits found in Arizona, Utah, and California, often associated with hot spring activity or cave systems.
Collecting tips
- Geological Context. Look for Green Onyx in areas with limestone bedrock, active or ancient cave systems, or around hot springs and geysers where calcium carbonate-rich waters are present or were historically active.
- Surface Indicators. Outcrops may appear as banded, often translucent, masses within limestone or as layered deposits in stream beds or near spring orifices. Look for areas with evidence of water flow and mineral deposition.
- Acid Test (Caution). Calcite reacts with dilute hydrochloric acid (HCl), producing effervescence (fizzing). A small drop of 5-10% HCl on an inconspicuous part of the rock will confirm it is calcite. Always exercise caution and wear appropriate safety gear when handling acids.
- Hardness Test. Calcite has a Mohs hardness of 3. It can be scratched by a copper coin (hardness 3.5) but will scratch a fingernail (hardness 2.5). This helps differentiate it from harder minerals like quartz (true onyx, hardness 7).
Quick Check
- Color:
- Green, often banded with white/cream/brown
- Luster:
- Vitreous to waxy
- Streak:
- White
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