The Alps are a source of minerals that have been mined for thousands of years. In the 8th to 6th centuries BC during the Hallstatt culture, Celtic tribes mined copper; later the Romans mined gold for coins in the Bad Gastein area. Erzberg in Styria furnishes high-quality iron ore for the steel industry. Crystals are found throughout much of the Alpine region such as cinnabar, amethyst, and quartz. The cinnabar deposits in Slovenia are a notable source of cinnabar pigments.