What Is Arkose Sandstone? How Does it Form and Where?
Arkose is a detrital sedimentary sandstone with over 25% feldspar. It comprises mainly quartz and feldspar clasts with minor amounts of mica and some heavy
Mcnair, B.
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
What Are Pele’s Tears and How Do They Form?
Pele’s tears are small jet-black teardrop, obovoid, spherical, or cylindrical-shaped volcanic glass droplets formed when tiny blobs of ejected magma cool quickly. They often precede
How Do the Mystical Pele’s Hair Form?
Pele’s hair is a formal geological term that volcanologists give to the golden-brown, fiber or thread-like strands of volcanic glass formed naturally from blowing out
What Are Inselbergs (Monadnocks) and How Do They Form
Inselberg or monadnock (pronounced /məˈnædnɒk/) in geology, geomorphology, or geography refers to an isolated, steep-sloped ridge, hill, small mountain, or knob sitting in a relatively