Ferruginous Quartz is a quartz that is evenly coloured in yellow, red, or brown tones by inclusions of iron compounds, usually iron oxides and hydrous iron oxides. Some types of natural stone can acquire rust stains. This is due to the chemical composition, rust composition, and molecular structure of the hardscape material.
When you find rust-like colours or veins in stones, it’s very likely that there’s an iron deposit present in the stone. Sometimes the iron deposits are not on the surface but instead found underneath a few layers of the stone.