Malachite is a copper carbonate, and it is three quite different things at once: an ore, a pigment, and a stone worked at architectural scale.
As an ore it is where copper was first found. Malachite is a secondary mineral forming in the oxidised upper part of a copper deposit, it is unmistakably green, and it smelts easily. It is the most likely candidate for the first metal ore anyone reduced, and prospectors have used its green stain as a surface indicator for five thousand years.
As a cosmetic and pigment it is the green eye paint of Egypt. Egyptian eye paint came in two colours: green from ground malachite and black from galena, a lead sulphide, and both are found in tomb assemblages with the palettes used to grind them. As an artists' pigment malachite gives a fine green that is difficult to handle, since grinding it finely enough for a smooth paint destroys the colour.
Its most spectacular use is Russian. The Ural deposits yielded masses of banded malachite large enough to work at scale, and the technique developed for it, sometimes called Russian mosaic, veneers thin slices onto a shaped core with the banding matched across the joints, so that a column or a table appears to be carved from a single impossible block. The Malachite Room of the Winter Palace in Saint Petersburg is the showpiece.
Malachite is soft, it takes a good polish, and copper carbonate dust is not a benign material to grind, which the workshops knew.