Kyanite is a common metamorphic silicate mineral, usually bluish in color, though it can appear in shades of grey, black, blue, pink, white and yellow. It is usually found as bladed crystals, though radiating masses of crystals have been known to occur. Kyanite can expand up to twice its original volume when heated.
Chemical composition: Al2(SiO4)O; Hardness: 5.5-7
Silver was known as Argentum in ancient Rome, thus its abbreviation as Ag. It is a member of the copper group.
Chemical composition: Ag; Hardness: 2.5-3