Grades of Lava

The USGS inspects lava and gives it a grade - e.g. prime (glassy, solid), choice (smooth, some air pockets), select (less smooth, distinct holes), standard (rough, broken), and ropy. Ropy lava looks like it came from the hindquarters of a volcanic animal.

Favorite igneous rocks #1 - Volcanic Bomb

An unexploded volcanic bomb.

Discovery

Igneous rocks were discovered in 633 AD by Captain Horatio Hornblende ("The Jaunty Pirate"). "Aaargh! What be this typically opaque green, greenish-brown, brown or black color rock?"

Two more types of igneous rocks

Igneous rocks can also be divided into hazardous (like lava and volcanic bombs) and non-hazardous (rocks you can sit on).

Two main types of igneous rocks

Geologists divide igneous rocks into two types - obtrusive and unobtrusive. Obtrusive igneous rocks stick out of the ground, and can be a tripping hazard or even mountainous. Unobtrusive rocks are underground.

Why do I like Igneous Rocks? It's ignementary. Lava, volcanoes, and all that.