Allophane - Al₂O₃(SiO₂)₁.₃-₂.₀·2.5-3.0H₂O

Habit: White, pale blue to sky blue, green or brown. Hyaline crusts and masses, stalactites or flowstones. Vitreous to earthy or waxy luster; translucent. White streak.

Environment: Found in hydrothermally altered igneous rocks, from the breakdown of feldspars, and in hydrothermal veins.

Etymology: From the Greek words for "other" and "to appear," referring to its change of appearance under a blowpipe.