What is it?
Quartz is chemically silicon dioxide (SiO2) thus containing 46.74% Silicon and 53.26% oxygen by weight. It is the most abundant mineral on the Earth. It is found in almost every geological environment and also it is at least a component of almost every rock type.
Quartz is a three dimensional network of silica tetrahedra as shown above.
Quartz is mostly crystalline in its arrangement though it may vary in the extent of crystallization. The macro-crystalline variety is the one in which the individual crystal is visible to the unaided eye. The other variety is micro-crystalline or cryptocrystalline, in which aggregates of crystals are visible only under high magnification. The transparent variety tends to be macro-crystalline and the cryptocrystalline varieties are either translucent or mostly opaque.
Note: The same molecular structure, if amorphous in arrangement is very different in properties and is thus termed as glass not quartz.
- Tactile properties: It is rough and abrasive
- Visual properties:
- Color: It is clear in pure form.
- Lustre: It is vitreous, waxy and dull.
- Streak: It is white.
- Diaphaneity: It is transparent.
- Structural properties:
- Hardness: 7 mohs.
- Specific gravity: 2.65
- Affinity to water: Quartz can adsorb water. To some extent it can even absorb water either evenly in the form of tiny dispersed bubbles or the form of randomly distributed droplets. It is insoluble in water. However, in powder form it can disperse in water.
- Affinity to oil: Quartz has low oil absorption capacity.
- Heat properties:
- Coefficient of Thermal Expansion: 5.5×10 -7 cm/cm °C (20°C-320°C)
- Thermal Conductivity: 1.4 W/m . °C
- Specific Heat: 670 J/kg . °C.
- Decomposition: M.P
- Electric properties: It does not conduct electricity.
- Combustion properties: It is non explosive and non inflammable.
- Chemical properties: Strong reducing agents like carbon can convert it to silicon. Further, it reacts only with very strong acids. With strong alkalis it reacts to form silicates.