Question

How does amorphous silica differ from quartz?

Answer 1

Amorphous solid: It is a type of solid in which the constituent particles do not have a regular three-dimensional structure or arrangement. These solids are isotropic in nature i.e., the physical properties it consists, are identical in all directions.
Crystalline solid: It is a type of solid in which the constituent particles have a regular geometry and three-dimensional structure. These solids are anisotropic in nature i.eThe physical properties it consists, are not identical in all directions.

Complete answer:
Silica: It is the key source of silicon. The silicon atom is never found as a free element in earth’s crust; therefore, silica is present in the form of silicon dioxide i.e., $Si{O_2}$. It is an amorphous solid i.e., possesses short range order and no definite geometry of constituent particles.
It is a white powdered solid whose $Si{O_4}^{4 - }$ ions are randomly connected to form polymeric chains or units.
Quartz: It is a crystalline solid having an overall chemical formula of $Si{O_2}$. In the structure of quartz, all atoms are linked in a continuous framework of $Si{O_4}^{4 - }$ i.e., silicon-oxygen tetrahedron. Due to its crystalline nature, it has a sharp and definite melting point and consists of long-range order.
Therefore, both quartz and silica are made of silicon dioxide but differ in the physical and chemical properties.

Note:
Silica is the pure form of silicon dioxide whereas the quartz may have a mixture of other minerals. Cristobalite is known as one of the allotropic forms of silica having the same molecular formula like quartz but differ in chemical structure. Quartz is abundantly found in various types of rocks like igneous, sedimentary and metamorphic rocks.