Also fishtail twins are quite interesting as well. Dimorphous minerals are minerals that share the same chemistry, but have different structures. Epididymite's structure is orthorhombic and eudidymite's structure is monoclinic , symmetrically speaking. Color is usually white or colorless, but can be pale gray, blue, yellow or violet. Luster is vitreous to silky.
Crystals are transparent to translucent.
Crystal System is orthorhombic. Crystal Habits include fibrous, acicular and prismatic habits, but more commonly found as tabular, somewhat elongated crystals and aggregate spherulites. Fracture is splintery to uneven. Hardness is 6 - 7. Streak is white.