What is the typical carat value of gold used in jewelry?

What is the proportion of gold and copper in $22$ carat gold ornaments?

Name two metals which have very low melting points.

When finely powdered ore is placed on a rotating grooved table and rotated rapidly,the lighter impurities are removed. What is this method of concentration called?

What is the molecular formula of cryolite?

Why should metal sulphides and carbonates be converted to metal oxides during the process of metal extraction?