► Ores
Ores are naturally occurring rocks or minerals from which valuable metals or other elements can be extracted profitably. For example, bauxite is an ore from which aluminum is extracted, and hematite is an ore from which iron is obtained.
► Gangue
Gangue refers to the unwanted or worthless materials that are found alongside the valuable minerals in an ore. These impurities are separated from the ore during the refining process to obtain the pure metal. For example, in the case of hematite (iron ore), silica and clay are common gangue materials.
► Rust
Rust is a reddish-brown substance that forms on the surface of iron or steel when it reacts with oxygen and moisture in the environment. Chemically, rust is iron oxide (Fe₂O₃·nH₂O) and is a form of corrosion that weakens the metal over time. For example, an iron nail left exposed to air and moisture will develop rust.
► Aqua Regia
Aqua regia is a highly corrosive mixture of concentrated nitric acid (HNO₃) and hydrochloric acid (HCl) in a 1:3 ratio. It is capable of dissolving noble metals like gold and platinum, which do not dissolve in other acids. For example, gold, which is inert in most acids, dissolves in aqua regia.
► Anodizing
Anodizing is an electrochemical process that increases the thickness of the natural oxide layer on the surface of metal parts, typically aluminum. This process enhances corrosion resistance, surface hardness, and allows for the application of colored dyes to the metal. For example, anodized aluminum is often used in electronic devices and architectural applications due to its durability and aesthetic finish.