2007-03-05 11:11:51 · 6 answers · asked by Anonymous in Science & Mathematics ➔ Earth Sciences & Geology
Black glass is also called obsidian. It is a glassy rock of volcanic origin of intermediate to acid composition formed by the chilling of rhyolite lava.
Intermediate means- a rock with <10% quartz plus plagioclase and or an alkali feldspar.
Acid means- an igneous rock with <10%free silica
2007-03-05 12:20:48 · answer #1 · answered by Professor Kitty 6 · 0⤊ 0⤋
It is called Obsidian. The mineral is quartz.
It is composed of Silica (SiO2) and minor portions of other elements. The reason for the glass shape is a result of rapid cooling. Usually found near volcanoes. The rapid cooling of magma (lava when ejected from the volcano) does not allow the elements' electrons to line up. The material cools so quickly that the ions are locked into position and appear to look like glass. When classifying this type of mineral, the material would have what is called "conchoidal fracture"
If given the time to cool slowly, the chemical makeup will be very similar but look very different.
2007-03-05 20:03:28 · answer #2 · answered by flyerave 3 · 0⤊ 1⤋
Obsidian.
2007-03-05 20:15:05 · answer #3 · answered by Anonymous · 0⤊ 0⤋
I believe you are looking for obsidian
2007-03-05 19:15:53 · answer #4 · answered by Controlfreak38 6 · 1⤊ 0⤋
http://pl.wikipedia.org/wiki/Obsydian
2007-03-05 19:15:53 · answer #5 · answered by Rando 4 · 0⤊ 0⤋
hematite
2007-03-05 19:15:21 · answer #6 · answered by medsans1 2 · 0⤊ 1⤋