Syenite: A Coarse-grained Granite-Like Plutonic Rock
Syenite is a coarse-grained, mostly light-colored intrusive rock with an intermediate to felsic composition. It has mainly alkali feldspar, lesser plagioclase, and one or more
Igneous
Everything You Ought to Know about Andesite Rock
Andesite is a fine-grained, intermediate volcanic or extrusive igneous rock. Its composition lies between basalt and dacite, and it has mainly sodium-rich plagioclase and one
Diorite: A Salt-and-Paper Looking Coarse-Grained Rock
Diorite is a coarse-grained, intermediate plutonic, or intrusive igneous rock. It has mainly plagioclase feldspar, biotite, hornblende, sometimes pyroxenes, and other minerals. This rock’s composition
Dunite: A Coarse-grained, Olivine-rich Greenish Plutonic Rock
Dunite is a coarse-grained, pale green to olive-green, ultramafic intrusive igneous rock with more than 90% olivine. It also may have smaller amounts of pyroxene,
Obsidian: A Hard, Brittle Natural Volcanic Glass or Rock
Obsidian is a felsic, naturally occurring volcanic glass. It has 69-77% silica and is relatively high in alkalis (>7%) and low in iron and magnesium
A Complete Guide to Rhyolite: A Common Light-colored Volcanic Rock
Rhyolite is a highly silicic, fine-grained, light-colored volcanic or extrusive igneous rock. It is a felsic rock with mainly quartz, alkali feldspar, plagioclase, and minor
Pumice: A Frothy, Light-Colored Volcanic Rock with Many Uses
Pumice is a very low-density, form-like, mostly light-colored glassy volcanic rock with a vesicular texture, not a mineral. This rough, porous rock forms from mostly
Understanding Scoria: A Highly Vesiculated Dark-Colored Volcanic Rock
Scoria is a mafic to intermediate highly vesiculated dark gray, black, reddish, or brown extrusive igneous rock (volcanic glass). This vesicular textured pyroclastic rock forms
What Are Apache Tears or Obsidian Balls?
Apache tears (marekanite or obsidianites) are smoky, dark gray, gray-brown, or black indented tear-shaped, rounded, or subangular small obsidian balls, pebbles, or nodules measuring up