Most of it occurs in the Eastern Goldfields area near the towns of Leonora, Kalgoorlie and Norseman.
Dendritic Moss Agate is a variety of Chalcedony with tree-like natural inclusion in the opal stone, and frequently containing green mineral inclusions, such as Chlorite, Hornblende, etc., or brown to black dendrites of Iron or Manganese Oxides.
It's a name given to any common opal with a tree or fern like silicates or manganese oxides. The Mohs scale in hardness is 7.
This listing is for a chunk of Dendritic Moss Agate originating from the mining area called Grant's Patch, 50 km North West of Kalgoorlie, Western Australia. It measures approx. 107 x 78 x 49 mm at widest points, and weighs 342 g.