Mercury(II) oxide, typically orange-red to red. Due to extreme mercury toxicity, it has no metaphysical use and is of interest mainly to mineral collectors specializing in hazardous materials.
Orange-Red, Red, Brownish-Red
Montroydite is classified as a oxide mineral mineral which typically crystallizes in the orthorhombic system. Its chemical formula is HgO. Common crystal habits include long prismatic, equant, rarely flattened; striated; massive to vermicular clusters.