Where is Andesite found?
Andesite
Got a photo? Identify rocks instantly with the Rockby app
Open the appAndesite 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 Andesite
Andes Mountains, South America
The type locality for andesite, where it is extensively found along the entire length of the mountain range, forming numerous volcanoes.
Cascade Range, North America
Prominent volcanoes like Mount St. Helens, Mount Rainier, and Mount Hood are largely composed of andesite and dacite.
Japan
Many of Japan's active volcanoes, part of the Pacific Ring of Fire, erupt andesitic lavas.
Indonesia
Numerous volcanoes in the Indonesian archipelago, such as Mount Merapi, are known for their andesitic eruptions.
New Zealand
Volcanic centers in the North Island, including Ruapehu and Ngauruhoe, are predominantly andesitic.
Collecting tips
- Look for Volcanic Terrains. Andesite is found in areas of active or geologically recent volcanism, particularly stratovolcanoes and volcanic arcs.
- Examine Outcrops. Look for dark to medium-gray, fine-grained rocks that may contain visible crystals (phenocrysts) of light-colored plagioclase or dark mafic minerals.
- Check for Flow Structures. Andesite lava flows can exhibit flow banding or columnar jointing. Pyroclastic deposits (tuffs, breccias) may also contain andesitic fragments.
- Consider Associated Rocks. Andesite often co-occurs with dacite, rhyolite, and volcanic breccias in arc settings.
Quick Check
- Color:
- Gray to dark gray, sometimes reddish-brown or black.
- Luster:
- Dull to earthy groundmass, vitreous phenocrysts.
- Streak:
- White to light gray (due to the dominance of silicate minerals).
Explore Andesite
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.