HYALITE is a clear variety of Opal that forms globules or clusters of globules becoming botryoidal[it resembles a bunch of grapes.] This specimen was found in the flat top mountains near Dalby nsw Australia.These Hyalite specimens fluoresces green.I have included two photos of a specimen in my collection to show how it forms on rhyolite rock.
Weight 2.10 cts app
Size 9 x 8 x 7 mm app
This is a special type of opal which is often classified with common opal. Hyalite is, however, a very distinctive material. It is always colourless and glass clear, and contains less water than other forms of opal. Its water content is usually of the order of 3-4%. Hyalite is most commonly found in association with volcanic rocks, especially in small cavities, or vugs. It may also be found coating secondary minerals in the weathering zone of ore deposits.