Chrysocolla from Peru, "always fits" 4mm bullet bracelet.

The mineral chrysocolla is a hydrated copper aluminum silicate with the chemical formula (Cu, Al) 2H2Si2O5 (OH) 4n (H2O). The mineral belongs to the cyclosilicates. Translucent to opaque green, blue, blue-green or brown chrysocolla has a dull to glass luster, a light green stripe color and the mineral does not split. Chrysocolla has an average density of 2.15 and the hardness is 2.5 to 3.5. The crystal system is orthorhombic and the mineral is not radioactive. Similar minerals are dioptase, shattuckite and turquoise. The name of the mineral chrysocolla is derived from the Greek words chrysos ("gold") and kolla ("glue"). This name was given because the mineral was used to solder gold. Chrysocolla is a fairly common mineral that mainly occurs as an accompanying mineral to copper ores. The type location is Nizhne-Tagilsk in the Urals, Russia. There are significant concentrations in the United States, mainly in the states of New Mexico, Nevada, Arizona, Idaho and California. This mineral is also found in Mexico, Chile, Peru and Canada. Very beautiful stones come from Israel, South Africa, Congo, Zimbabwe, Russia, Kazakhstan, Moldova, Germany, England, Romania and France. Eilat stone is an intergrowth of chrysocolla with turquoise and malachite, found near Eilat in Israel. Chrysocolla quartz is an intergrowth of chrysocolla with quartz.