During the extraction of copper from copper pyrite,the flux used for the removal of ferrous oxide is:

Silica is added to roasted copper ores during extraction in order to remove

Extraction of gold $(Au)$ involves the formation of complex ions $X$ and $Y$ as shown in the reaction: $\text{Gold ore}$ $\xrightarrow{CN^-, H_2O, O_2} HO^- + X$ $\xrightarrow{Zn} Y + Au$. $X$ and $Y$ respectively are:

The reaction for obtaining the metal $(M)$ from its oxide $(M_{2}O_{3})$ ore is given by
$M_{2}O_{3(s)} + 2 Al(\ell) \xrightarrow{\text{Heat}} Al_{2}O_{3}(\ell) + 2 M_{(s)}$, $(s = \text{solid}, \ell = \text{liquid})$
In this case, $M$ is

Which metal is leached from its ore using $KCN$?

Refractory materials are generally used in furnaces because