Extrusive Igneous Rocks
Mississippi Valley-Type (MVT) Deposits: The Complete Geological Guide
When it comes to the world’s major sources of lead and zinc, few geological formations are as significant as the Mississippi Valley-Type (MVT) deposits....
Andesite
What is Andesite?
Andesite is a fascinating extrusive igneous rock. Unlike intrusive rocks that cool slowly deep underground, andesite forms when magma erupts onto the...
5 Essential Facts About Sandstone…
The Earth's Porous Time Capsule and Ultimate Reservoir
What is Sandstone?
Sandstone is a clastic sedimentary rock composed primarily of sand-sized silicate grains. To a geologist,...
Phyllite
The Silky Transition in the Metamorphic Sequence
What is Phyllite?
Phyllite is a medium-grade, foliated metamorphic rock that holds a very specific place in the grand...
Hornfels
The Baked Rock of Contact Metamorphism
What is Hornfels?
Hornfels is a fine-grained, exceptionally hard, and non-foliated metamorphic rock. Its name derives from the German word...