Where is Onyx found?
Banded Chalcedony (SiO2)
Got a photo? Identify rocks instantly with the Rockby app
Open the appOnyx 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 Onyx
Brazil
Significant source of various chalcedony varieties, including onyx, often found in volcanic regions.
Uruguay
Known for high-quality agate and onyx deposits, particularly in basaltic flows.
India
Historical source of onyx and other chalcedony types, particularly in the Deccan Traps region.
Madagascar
Produces a range of chalcedony, including banded varieties.
Mexico
Sources of onyx, often associated with volcanic activity.
United States (Oregon, California, Arizona)
Various localities yield chalcedony, including some banded forms, often in volcanic terrains.
Collecting tips
- Look in Volcanic Terrains. Onyx frequently forms in the vesicles and cavities of basaltic and rhyolitic volcanic rocks. Search for geodes or amygdules in these areas.
- Examine Stream Beds and Gravel Pits. Weathering and erosion can release onyx nodules and fragments from their host rock, transporting them to stream beds and alluvial deposits.
- Identify Banding. The key identifying feature of true onyx is its straight, parallel banding. Look for distinct color layers.
- Check Hardness. Onyx, being a form of quartz, will scratch glass and steel (Mohs hardness 6.5-7). This helps differentiate it from softer look-alikes.
- Observe Luster. A waxy to vitreous luster on a fresh or polished surface is characteristic.
Quick Check
- Color:
- Banded (typically black/white, brown/white) or solid black
- Luster:
- Waxy to vitreous
- Streak:
- White
Explore Onyx
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.