Calcite forms in many different geologic environments. Usually colorless or white it can occur in many tints due to the inclusion of minor constituents during formation. It has possibly more habits of occurrence than any other mineral.
Chemical composition: Ca[CO3]; Hardness: 3; Trigonal
Hemimorphite is a white, pale blue-green or gray hydrous zinc silicate usually found in the oxidized zones of zinc and lead deposits, and often associated with smithsonite, ZnCO3. They were assumed to be the same mineral and both were classed under the same name of calamine. Some specimens show strong green fluorescence in shortwave UV light and weak light pink fluorescence in longwave UV.
Zn4Si2O7(OH)2 · H2O; Hardness 4½ - 5; Orthorhombic
Hematite is a common iron oxide that is sometimes magnetic. It is iron, grey in color and is found throughout the world near the earth’s surface.
Chemical composition: Fe2O3; Hardness: 5-6
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 the Johann Wolfgang von Goethe
α-Fe3+O(OH); Hardness 5 - 5½; Orthorhombic