Malachite

Malachite
Malachite from the Democratic Republic of the Congo
General
Category	Carbonate mineral
Formula (repeating unit)	Cu2CO3(OH)2
Strunz classification	5.BA.10
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/a
Identification
Formula mass	221.1 g/mol
Color	Bright green, dark green, blackish green, commonly banded in masses; green to yellowish green in transmitted light
Crystal habit	Massive, botryoidal, stalactitic, crystals are acicular to tabular prismatic
Twinning	Common as contact or penetration twins on {100} and {201}. Polysynthetic twinning also present.
Cleavage	Perfect on {201} fair on {010}
Fracture	Subconchoidal to uneven
Mohs scale hardness	3.5–4.0
Luster	Adamantine to vitreous; silky if fibrous; dull to earthy if massive
Streak	light green
Diaphaneity	Translucent to opaque
Specific gravity	3.6–4
Optical properties	Biaxial (–)
Refractive index	nα = 1.655 nβ = 1.875 nγ = 1.909
Birefringence	δ = 0.254
References

Malachite is a copper carbonate hydroxide mineral, with the formula Cu₂CO₃(OH)₂. This opaque, green banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fractures and spaces, deep underground, where the water table and hydrothermal fluids provide the means for chemical precipitation. Individual crystals are rare but do occur as slender to acicular prisms. Pseudomorphs after more tabular or blocky azurite crystals also occur.

The stone's name derives (via Latin: molochītis, Middle French: melochite, and Middle English melochites) from Greek Μολοχίτης λίθος molochitis lithos, "mallow-green stone", from μολόχη molōchē, variant of μαλάχη malāchē, "mallow". The mineral was given this name due to its resemblance to the leaves of the mallow plant.

Archeological evidence indicates that the mineral has been mined and smelted to obtain copper at Timna Valley in Israel for over 3,000 years. Since then, malachite has been used as both an ornamental stone and as a gemstone.

In ancient Egypt the colour green (wadj) was associated with death and the power of resurrection as well as new life and fertility. They believed that the afterlife contained an eternal paradise which resembled their lives but with no pain or suffering, and referred to this place as the ‘Field of Malachite’.