Chemical composition -- Lead chromate.
Color -- Red to orange.
Optics -- R.I 2.29-2.66.
Durability -- Hardness 2.5-3. Brittle.
Crystal structure -- Monoclinic.
Specific Gravity -- 5.9-6.1 (very dense).
Sources -- Tasmania is the best known source of this rare material. The intense red to orange color makes spectacular collector stones, but cutting is difficult.