glassy igneous rocks

SRI Petrography ID: 9

Names

[de] Glasige magmatische Gesteine
[en] glassy igneous rocks

Description

A glassy igneous rock consists of dense volcanic glass. The very porous, foamy variety is called Pumice.

The most important rock type belonging to this group is:
obsidian

Color

mostly dark (black, brown), but also grey (if containing gas bubbles or water)

Grain Size

glassy, no crystals

Texture

no texture, sometimes laminated (flow texture)

Minerals

no macroscopic visible minerals

Occurences

Iceland, Italy (Eolian Islands), Greek islands (Santorini, Aegina,..)

Classification

Class

IGNEOUS ROCKS

Narrower Terms

obsidian