Quartz
Topic: Minerals, Rocks and the Rock Cycle · NCERT: Beyond NCERT
Meaning
Quartz is a mineral made of silica, which is silicon joined with oxygen. It is hard (7 on the Mohs scale), so it scratches glass. It is usually white or colourless and does not dissolve in water. Because it resists weathering (the breaking down of rock by weather), quartz grains survive long after the other minerals in a rock have broken down. That is why quartz is the main grain in sand and sandstone. It is used to make glass and electronics, and its crystals keep time in watches.
Example
The granite domes and tors (piles of rounded boulders) around Hampi, Karnataka are rich in quartz and feldspar. As this granite weathers, the quartz grains are left behind as sand.
Don't confuse with
- Quartzite: quartz is a single mineral. Quartzite is a metamorphic rock that forms when sandstone is changed by heat and pressure. It makes ridges like the Aravallis and the Delhi Ridge.