Darwin Glass is not a mineral but a frothy siliceous pale green to black glass known as impactite, formed from a meteorite collision with siliceous rocks near Mt Darwin, and related to tektites. It is widespread in small amounts on the eastern slopes of Mt Darwin and is most abundant on the eastern slopes of Ten Mile Hill, 20 kms south-south-east of Queenstown. The glass is very irregular, slaggy, with twisted stalactitic forms and with rare teardrop and disc-like shapes. Numerous bubble pits are present and the pieces are consequently of very low density (specific gravity 1.7-2.2) and have a contorted appearance well described by the prospectors term “petrified kelp”. The source crater (astrobleme) is the Darwin Crater, east of Mt Darwin, but no Darwin glass can be found within this weathered structure.
