© Copyright, 2000, All Rights Reserved by Rob Kanen.
Agates are popular among collectors for their attractive appearance. Victoria has several prominent agate and geode localities associated with volcanic rocks. Agates are a form of chalcedony and are deposited by fluids that infiltrate voids in volcanic rocks. They often have attractive banding and star shaped patterns. Geodes have a hollow interior usually filled with crystals of smoky quartz, quartz and amethyst.
The Wellington Rhyolite, near Bairnsdale, is the prominent agate field in Victoria. The agates are usually grey chalcedony with a cream to light brown matrix. The gates can be found in the Mitchell River and in streams near Briagolong, where they form hard, rounded nodules and pebbles. They are often banded with star patterns and crystalline centres.
Small chalcedony filled agates also occur at Kitty Miller Bay on Phillip Island. Here, they form small round and elliptical nodules. These agates are hosted by basalt rocks which are widespread along the coast between Phillip Island and the Mornington Peninsula. These basalts are also hosts to zeolite occurrences.
Mooroka, in Western Victoria, is notable for its geodes. The geodes at Mooroka are hosted by rhyolite and they consist of a hard chalcedony nodule lined on the inside with tiny quartz crystals. Large smoky quartz crystals usually fill the hollow centre.
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