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Identifying Minerals-Colour.

Identifying Minerals-Colour- Hardness-Density.

When Identify a mineral-stone-rock you have picked up can be easy or  very hard to Identify.

A Crystal structure and chemical composition of the mineral can determined  the certain physical properties. such as hardness and density and colour.

The Properties.

The Properties, such as hardness and density, can be measured objectively, while others, such as colour and lustre, demand a more subjective assessment.

Mineral Colour.

 

Some Minerals have characteristic colours and others do not. The bright Blue of azurite, the Yellow of sulphur, and the green of Malachite allow an almost instant identification. At the other end of the scale, fluorite occurs in virtually all colours, so it can only be identified by observing other of its properties.

Colour in Minerals  is caused by the absorption or refraction of light of particular wavelengths. This can happen for a number of reason. One is the presence of foreign atoms-atoms not part of the chemical makeup of the mineral. crystal structure. These are called trace elements.  The colour produced by a particular trace element varies according to the mineral it inhabits.

Chromium is the colouring element in both red ruby and green emerald. Colour can also result from the absence of an atom or ionic radical from a point that would normally occupy in a crystal. These types of defects are called vacancies, and their result is called a colour centre. The violet colour of the fluorite is produced by a vacancy.

Identifying Minerals- Fluorite.

Due to the many colour variations of fluorite, it can resemble a variety of gemstones; however, it can be easily distinguished by its relatively low level of hardness. Some possibilities for confusion include calcite, but calcite is slightly softer and has a different crystal form. Quartz is much harder and lacks the cleavage of fluorite, while apatite is slightly harder and has a different crystal form. Another distinguishing characteristic of fluorite is its property of thermoluminescence; the ability to glow when heated. One variety of fluorite known as ‘chlorophane’ demonstrates this well and can display thermoluminescence even when held in the hand. The thermoluminescence is green to blue-green.

orange calcite
Calcite Rhomb White

The Structure .

The Structure of the mineral itself, without any defects or foreign elements, may also cause colour .

Opal

The Opal Stone is composed of minute spheres of silica that diffract light, while the colour and sheen of moonstone is determined by the thin interlayering of two different feldspars. In some crystals, light vibrates in different planes within the crystal, with the result that, whatever the initial cause of its colour may be appears as different colours when observed along different axes. This is called Pleochroism.

 

Mineral Lustre

The Mineral Lustre is the general appearance of its surface in reflected light. Two types of lustre: Metallic and Non- metallic.

Metallic. Lustre is that of an untarnished metal surface, such as gold, steel, or copper. Minerals with metallic lustre  are opaque to light, even on the edges.

Minerals with non-metallic lustre are generally lighter in colour and show some degree of transparency or translucency, even though this may only be on a thin edge.  Terms which describe non-metallic lustres, vitreous, having the lustre of a piece of broken glass, adamantine, having the brilliant lustre of a diamond, resinous, having the lustre of a piece of resin, pearly, having the lustre of pearl or mother of pearl, greasy, appearing to be covered with a thin layer of oil, silky, appearing as the surface of silk or satin, dull, producing little or no reflection and earthy, having the non-lustrous appearance of raw earth.

Vitreous.   Many Silicate Minerals like Quartz Crystal have a vitreous lustre and appear similar to glass surface.

Greasy.    Orpiment can have a greasy or a resinous lustre.

Resinous.–Not quite glassy the Look of Amber –

Silky. — The look of silk, fine parallel fibers of mineral – such as chrysotile “asbestos”;

Dull.–A plain looking surface

Earthy.–Having the look of soil or clay.

 

Is it a Diamond.

A diamond can be Identified by a range of properties, It hardness, its lustre, its perfect cleavage, and its high refractive index, which makes it disperse white light. Diamond is the hardest gemstone. I have never found one but they say you will know from the light/beauty  the stone  will display.

Is it Gold.

Well the colour is gold, gold is heavy, It does have shin to it.  The gold you see in Jewellery, only a small percentage is gold. 

 

More information Coming soon. Contact me

Have a great day.

 

 

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