Where is Rhyolite Porphyry found?
Rhyolite Porphyry
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Open the appRhyolite Porphyry 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 Rhyolite Porphyry
North America
Western United States (e.g., Yellowstone region, Cascade Range, Basin and Range Province), Canadian Cordillera, Mexico (Sierra Madre Occidental).
South America
Andes Mountains (e.g., Chile, Argentina, Peru, Bolivia).
Europe
Italy (Tuscany), Germany (Saxony), Scotland, Iceland.
Asia
Japan, Indonesia, parts of China and Russia.
Oceania
New Zealand, Eastern Australia.
Collecting tips
- Look for Volcanic Terrains. Rhyolite porphyry is found in areas of past or present felsic volcanism. Look for ancient volcanic fields, calderas, and lava flows.
- Examine Outcrops for Texture. The key identifying feature is the porphyritic texture. Look for larger, distinct crystals embedded in a fine-grained matrix. Weathered surfaces might highlight the phenocrysts.
- Check for Flow Banding. The presence of flow banding (parallel layers or streaks of different colors or textures) is common in rhyolites and can be a good indicator.
- Assess Color and Hardness. Rhyolite porphyry is typically light-colored and hard. Test its hardness with a steel tool (it should scratch steel).
Quick Check
- Color:
- Light (pink, red, gray, cream, green)
- Luster:
- Dull to vitreous (groundmass), vitreous to pearly (phenocrysts)
- Streak:
- White
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