This pair of earrings is crafted from solid Sterling Silver and features a pair of Natural Boulders Opal from Australia, which is stamped with the 925 mark. The Opal industry classifies Boulder Opal as a Natural Opal Type 2, indicating that it is attached to a host rock with a distinct chemical composition. Genuine Natural Australian Boulder Opal is made up of hydrated amorphous concretions of SiO2nH2O silica, composed of silicon dioxide molecules arranged in closely packed planes that fill the crevices of Boulder Opal ironstone. This type of Opal is exclusive to remote areas of Queensland, Australia, and is a rare resource that has reputedly increased in value up to 15% annually. The pendant is guaranteed to be devoid of artificial coloring or dyes All Australian Opal Cutters Jewellery and Loose Opal items are covered by our international warranty. Please send us an note when you check out if you would like to add any modifications or changes or have a specific colour requirement for your Opal. On request and at an additional charge we are able to change or upgrade your Opal (or change the design) of any item that we offer. The item shown online may not exactly reflect the item you receive as Opals have a living play of colour that can be difficult to capture on camera.