Malachite

Malachite is a mineral.

Source
Malachite is a mineral that miners can extract from Copper Veins. However, the chances of actually getting it by mining copper is approx 1%.

Other potential sources include mob drops, prospecting on Copper Ore, and chests.

Malachite as an Ingredient
Malachite is used in the following recipes:

Blacksmithing

 * Copper Battle Axe
 * Copper Chain Vest
 * Gemmed Copper Gauntlets

Engineering

 * Crude Scope
 * Deepdive Helmet
 * Gnomish Universal Remote
 * Mechanical Squirrel Box

Jewelcrafting

 * Bronze Band of Force
 * Inlaid Malachite Ring
 * Malachite Pendant