Typical glass is made of about 75% silica (SiO2) Na2O, lime (calcium oxide - CaO), magnesium oxide (MgO) and aluminum oxide (Al2O3) and some other additives.
The three minerals that are metals and can scratch glass are iron pyrite (pyrite), hematite, and magnetite. These minerals have a high hardness level, allowing them to scratch glass and show metallic luster.
Glass
magnifying glass
magnifying glass
There are no minerals in pumice, just glass, but there is a high level of silica.
Diamond
No minerals make up true volcanic glass, as the crystalline structure of minerals did not have time to form before the lava hardened. A mineral must have a crystalline structure.
apatite with a steel knife feldspar with window glass
For glass, plastic and so on
They are not naturally occurring
No. It is vesicular glass, like pumice.
No, it is a colloidal glass.