A good test in those cases is the knife test in which a knife blade when scratched across the surface of the sample will produce a powder in halite and not in sylvite. The name sylvite is easily confused with the much more valuable sylvanite . Sylvanite is a silver gold telluride , AuAgTe 4 and should never be mistaken for sylvite. Color is colorless or white, sometimes tinted red, blue or yellow. Luster is vitreous.
Crystals are transparent to translucent.
Crystal Habits are cubes with frequent octahedral faces truncating the corners of the cube, crystals will often have a cavernous appearance from dissolution. More commonly massive and granular. Cleavage is good in three directions forming cubes. Fracture is uneven. Streak is white.