Meteorite Glossary - Letter I

Igneous Rocks:

Rocks that form by heat and melting. The two types of igneous rocks are volcanic and plutonic. Volcanic rocks as the name implies are eruptive rock, like lavas. Plutonic igneous rocks form below the surface by the slow cooling of rocks at great depth. Volcanic rocks are fine grained because of quick cooling. Not time for crystals to grow more than microscopic in size. Plutonic igneous rocks have larger crystals through very slow cooling and long growth times.

Impactite:

A glassy rock that is found in association with impact structures and craters, it is formed from the melting of native rocks during the impact of asteroids. It can be very well melted found as glassy and solid or may be poorly melted and bubbly. sometimes it will contain spheroids of nickel iron from the impacting body.

Iridium:

A rare metallic element. It is found in meteorites, especially iron meteorites.