opalized wood, sterling silver, fine silver
Opal is a very interesting stone. It's formed when silica gel finds its way into crevices within a larger rock. As the water in the gel evaporates, silica left behind in the form of tiny spheres. Overtime, those spheres crystallize to form opal. Wood opal occurs when organic material in trees decays and is replaced with opal.
Silver, oh silver. This lustrous white metal is amazing - more reflective than gold, more conductive than copper and just plain gorgeous. When used for jewelry, silver is mixed with copper or zinc to provide more durability and reduce tarnishing. Fine silver is 99.9% silver while sterling silver is 92.5%. Other alloys are used for specific processes, such as reticulation (80% silver). All silver will tarnish over time, but can be easily cleaned and polished.