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AGATE

AMAZONITE

AMBER

AMETHYST

AVENTURINE

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Agate:

 

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Amazonite:

Amazonite is a potassium aluminium silicate mineral of the alkali Feldspar group, and is also known as Microcline. Microcline is a common mineral found worldwide, the massive form is green and green and cream striped (Albite) in colour. Amazonite crystals and twins are rare and are sought after by collectors and are often associated with Smokey Quartz.

Colour: Shades of green, cream

Class: Silicate, Potassium Feldspar

Group: Triclinic

Formations: Tabular crystals, grainy and compact massive; twinned crystals

Localities: Worldwide

Chemical Composition: KAISi₃O₈

Hardness: 6

Lustre: Vitreous, translucent to opaque

Cleavage: Perfect in one direction, good in another

Varieties: Microcline, Perthite 

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Amber:

Amber is fossil resin or tree sap that although not mineralised, it is sometimes considered a gemstone. Most of the world’s amber is in the range of 30-90 million years old. Semi-fossilzed resin or sub-fossil amber is called Copal. Amber rangers in colour from pale yellow, orange, green and even black. Amber can contain many preserved insects, animals and plants and this increases the value. Amber is often counterfeited with plastic resin.

Colour: Amber, yellow, orange, green, black

Class: Amorphous Mineraloid

Formations: Resinous nodules, often found with insects and vegetation inclusions.

Localities: Worldwide

Chemical Composition: C₁₀H₁₆0

Hardness: 2

Lustre: Resinous, translucent to transparent

Cleavage: None

Varieties: Succinite

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Amethyst:

Amethyst is the purple variety of Quartz, its colouration due to ferrous iron impurities. Amethyst is abundant with characteristics indicative of its locality. Russian Amethyst is uniform dark to medium. Amethyst is popular among collectors in its raw crystalline form (geodes, clusters, points); carved as spheres, tumblestones, wands, figures; and for its use in jewellery. Amethyst exists as double terminates, elestials, with inclusions and phantoms.

Colour: Light to dark purple

Class: Silicate

Group: Hexagonal, rhombohedral terminations

Formations: Clusters of pyramids on a geode base. Also occurs as tall prismatic crystals, short stubby crystals, in drusy aggregates, massive, in geodes, and as rounded river worn stones.

Localities: Worldwide

Chemical Composition: SiO₂ minor Fe⁴ impurities

Hardness: 7

Lustre: Vitreous, translucent to transparent

Cleavage: None

Varieties: Brandberg, Cactus, Chevron, Lavender, Veracruz

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Aventurine:

Aventurine is a form of Quartizite sedimentary rock deposit, characterised by its translucency and the presence of mineral inclusions that give a shimmering or glistening effect. Inclusions of Fuchsite Mica form spangled silvery green or blue Aventurine and Hematite or Goethite inclusions form a red or preach Aventurine.

Colour: Blue, green, peach, red, white

Class: Silicate

Group: Hexagonal

Formations: Massive aggregate of interlocking quartz grains

Localities: Worldwide

Chemical Composition: SiO₂ – K(AI,Cr)₂AISi₃O₁₀(OH)₂

Hardness: 7

Lustre: Vitreous, opaque

Cleavage: None

Varieties: Blue, green, peach, red, white Aventurine

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