Habit: Shades of yellow and orange, rarely deep red, single-ended pyramidal crystals and can also be prismatic and tabular, or as earth coatings. Resinous to Adamantine Luster, nearly opaque to translucent.
Environment: Is an alteration product of cadmium-bearing minerals, and forms earthy coatings on sphalerite and other zinc minerals. Also rarely forms crystals in cavities in mafic igneous rocks and in high temperature Hydrothermal vein deposits.
Etymology: Named for Lord Greenock (Charles Murray Cathcart, 1783-1859) who discovered it in Scotland