Aurichalcite is a rare, carbonate mineral usually found as a secondary mineral of zinc and copper deposits, often present as druzy crusts or aggregates of prismatic crystals. The color is usually bluish-green.
Chemical formula: (Zn,Cu)5(CO3)2(OH)6
Hardness: 1-2
Goethite is the yellow- or reddish-brown alpha polymorph of iron (III) oxide-hydroxide, typically occurring in low-temperature environments. Goethite has been well known since ancient times for its use as the pigment brown ochre. The mineral was named after Johann Wolfgang von Goethe.
α-Fe3+O(OH)
Hardness 5 - 5½
Orthorhombic
Gypsum commonly forms in several environments, ranging from sedimentary evaporite deposits to hydrothermal vein deposits. It can occur in massive granular form (alabaster), translucent white crystals (selenite is one variety), and as desert “roses.” It has extensive practical uses, such as fertilizer (for sulfur) and as building material (plaster of Paris, dry wall). Giant crystals of gypsum occur in Mexico’s Cave of Crystals and Cave of Swords.
CaSO4 · 2H2O
Hardness 2
Monoclinic