MINERALS: MOHS HARDNESS SCALE

BY: FERRAN GIL ESTELLER JOAN REVERTER VIVES DARIUS ANTONIO KOCZ-KISSJOSEP SÁNCHEZ QUERALT

MOHS HARDNESS SCALE

The Mohs hardness scales compares the resistence of a mineral to being scratched by ten reference minerals.The hardest mineral is the diamond (10)The softest mineral is the talc (1)

TALC (TALC)

Chemical composition: Mg3Si4O10(OH)2Position in Mohs scale: 1Habit: Crystal habitLuster: Waxlike or pearlyColour: Light to dark green, Brown, white, greyStreak: White to pearl blackDiaphaneity: TranslucentOther information: It is used by many industries

GYPSUM (GUIX)

Chemical composition: CaSO4·2H2OPosition in Mohs scale: 2Habit: Crystal habitLuster: Vitreous to silky, pearly, or waxyColour: Colorless to white; may be yellow, tan, blue, pink, brown, reddish brown or gray due to impurities.Streak: WhiteDiaphaneity: Transparent to translucentOther informations: Fragile toughness, low thermal conductivity

CALCITE (CALCITA)

Chemical composition: CaCO3Position in Mohs scale: 3Habit: Crystalline, granular, stalactitic, concretionary, massive, rhombohedral.Luster: Vitreous to pearly on cleavage surfacesColor: Colorless or white, also gray, yellow, greenStreak: WhiteDiaphaneity:Transparent to translucent.Other information: It may be fluorescent red, blue, yellow, and other colors under either SW and LW UV; phosphorescent.

FLUORITE (FLUORITA)

Chemical composition: CaF2Position in mohs scale: 4Habit: Crystal habitLuster: VitreousColor: Colorless, or different coloursIt depends on impuritiesStreak: WhiteDiaphaneity: Transparent to translucentOther information: Used in many chemical, ceramic and metallurgical processes

ORTHOCLASE (ORTOSA)

Chemical composition: KAlSi3O8Position in mohs scale: 6Habit: Crystal habitLuster: VitreousColor: Colorless, greenish, greyish, yellow, white, pinkStreak: WhiteDiaphaneity: Transparent to translucentOther information: it has got low negative relief

QUARTZ (QUARS)

Chemical composition: SiO2Position in mohs scale: 7Habit: Crystal habitLuster: VitreousColor: Colourless, or of different colours. It depends on impurities. Here, we have pink quartzStreak: WhiteDiaphaneity: TransparentAnother information: Its usefulness can be linked to its physical and chemical properties

TOPAZ (TOPAZI)

Chemical composition: Al2SiO4(F,OH)2Position in mohs scale: 8Habit: Crystal habitLuster: Vitreous Color: ColorlessStreak: WhiteDiaphaneity: Transparent to tranlucentOther informations: It has got ultraviolet fluorescence

CORUNDUM (CORINDÓ)

Chemical composition: Al2O3Position in Mohs scale 9Habit: Crystal habitLuster: Adamantine to vitreousColor: colourless, white, grey,brown, red, yellow, green, blue, violet. Streak :WhiteDiaphaneity: Transparent, translucent to opaqueOther characteristics:It may be fluorescent or phosphorescent under UV light

DIAMOND (DIAMANT)

Chemical composition: CPosition in Mohs scale: 10Crystal habit Luster :Adamantine Color :Typically yellow, brown or gray to colorless. Streak:ColorlessDiaphaneity: Transparent Other information :Diamond (the most valuable of all gems used by kings and famous ladies, causing fights and lust) is originally a coal: coal crystallized, if fire is applied to it, only ashes remain.