|
|
You are here:
Get Paid to Submit Articles Click Here
Gemstone Presentation
See More articles From peterhw
|
Gemstone Presentation.
Some gemstones maybe used in their natural or crystal form due to the very unusual or attractive appearance as they were found (sometimes seen as decorative table top item). Most stones are cut and polished for use as gemstones – as typically found in jewellry. There are two principal methods or processes for presenting the stones – and they are :-
• Stones which are ‘cut’ using a special faceting machine by grinding and polishing small flat surfaces called facets at regular intervals and angles around the stone.
• Stones which appear as a smooth ‘pebble or dome’ shape. These stones are called cabochons.
Stones which are opaque such as opal or turquoise are commonly cut as cabochons. These gems are designed to show the stone's colour or surface properties.
Gems which are transparent are normally faceted, which maximises the optical properties of the reflected and sometimes refracted light – this is what you may refer to as the ‘sparkle’ when you catch a diamond (for example) against the light. The facets must be cut at angles depending on the optical properties of the gem (i.e. a diamond would be cut with different facet angles to a ruby). If the angles are too steep or too shallow, the light will be refracted (i.e. through the stone) rather then reflected back to the observer.
Gemstone colour
Colour is the most obvious and attractive feature of gemstones. The colour of any material is due to the nature of light itself. Daylight, often called white light, is actually a mixture of different colours of light. When light passes through a material, some of the light may be absorbed, while the rest passes through. The part that isn't absorbed reaches our eye as white light minus the absorbed colours. A ruby appears red because it absorbs all the other colours of white light - blue, yellow, green, etc. - except red.
The same material can exhibit different colours. For example ruby and sapphire have the same chemical composition but show as different colours. Even the same gemstone can occur in many different colours: sapphires show different shades of blue and pink and "fancy sapphires" exhibit a whole range of other colours from yellow to orange-pink (called a "Padparadscha sapphire").
This difference in colour is based on the atomic structure of the stone. Although the different stones formally have the same chemical composition, they are not exactly the same. Every now and then an atom is replaced by a completely different atom causing impurities which are sufficient to absorb certain colours and leave the other colours unaffected.
|
See Peter
Williams @ The Article Sense
and also My Hampshire Blog
& Information Guide
Flag as inappropriate
| Comment |
|
| Share this article |
|---|
|
|
|
|
|
