Mexico/West Mexico
Epiclassic
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predominant temper is coarse altered sand
Altered Sand in Fine-Grained Matrix (AS-F) Fabric: 10-20% inclusions; 70-89% matrix; 1-10% voids
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polycrystalline quartz; plagioclase feldspar; fine-grained and coarse-grained volcanics
Sierra Madre Occidental
Coarse Altered Sand in Fine-Grained Matrix (Coarse AS-F)
rhyolitic ignimbrites