How Do Blocky Lava Flows Look Like and Form?
Block or blocky lava flows have a fragmented surface with large (usually up to a meter in size), angular to slightly smooth, or planar rubbles,
Felsic
A Detailed Guide into Nepheline Syenite Rocks
Nepheline syenite is a coarse-grained, pale-colored (white, gray, or pinkish) intrusive igneous rock that resembles granite. Its chemical composition is intermediate to felsic and has
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
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
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
Granite Pegmatites Texture Formation and Mineral Composition
Granite pegmatites are intrusive igneous rock with granitic composition and unusually large crystals, i.e., more than 0.4 inches (1 cm) with larger crystals more than 1.2 inches
Graphic Granite: A Unique Texture Resembling Ancient Cuneiform Writing
Graphic granite refers to granitic rocks with quartz-alkali feldspar intimate intergrowths whose texture or pattern resembles ancient cuneiform or runic writings or inscriptions. These rocks