State the role of silica in the metallurgy of copper and crydit in the metallurgy of aluminium.
Differentiate between roasting and calcination.

Explanation

### Step-by-Step Text Solution

**1. Role of Silica in the Metallurgy of Copper:**
- Silica, which is chemically represented as SiO2, acts as a flux in the metallurgy of copper.
- During the extraction of copper, silica combines with impurities such as iron oxide (FeO) to form a slag.
- The reaction can be represented as:
\[
\text{Cu} + \text{SiO}_2 + \text{FeO} \rightarrow \text{FeSiO}_3 \text{ (slag)}
...