Where is Agate in Rhyolite found?
Cryptocrystalline Quartz (SiO2) in Rhyolite
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Open the appAgate in Rhyolite 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 Agate in Rhyolite
Oregon, USA
Famous for thundereggs, particularly in areas like Richardson's Rock Ranch and the Ochoco Mountains, where rhyolitic flows are abundant.
New Mexico, USA
Various localities, especially in the southwestern part of the state, yield agate in rhyolite.
Mexico
Numerous deposits, particularly in states like Chihuahua and Durango, known for diverse agate varieties in volcanic hosts.
Germany
Idar-Oberstein region, historically significant for agate mining, often found in volcanic rocks.
Australia
Queensland and other states have occurrences of agate in volcanic rocks.
Collecting tips
- Look for Volcanic Terrains. Focus on areas with known rhyolitic lava flows, especially ancient ones that have undergone weathering and erosion.
- Identify Thundereggs. Search for spherical or nodular concretions that may have a rough, weathered exterior of rhyolite, often with a small 'navel' or protuberance indicating the former gas bubble.
- Check Weathered Outcrops. Agate is harder and more resistant to weathering than the surrounding rhyolite, so it may be found as float in stream beds or exposed on eroded slopes.
- Examine Road Cuts and Quarries. Fresh exposures of rhyolite can reveal embedded agate nodules.
Quick Check
- Color:
- Agate: Banded, varied; Rhyolite: Light, fine-grained
- Luster:
- Agate: Waxy to vitreous; Rhyolite: Dull to earthy
- Streak:
- White (for both agate and rhyolite)
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