Sapphire is one of the most durable, hardest and
scratch-resistant materials. It was first synthesized in 1902. The process of
making synthetic Sapphire is called as Verneuil
process. Only experts can differentiate between synthetic and natural Sapphire.
It offers a broad transmission range from Ultra Violet to mid infrared
wavelengths (250–4500 nm). The material is able to bear up extreme temperature
changes and environmental conditions.
The most valuable color of Sapphire is a cornflower
blue color, also known as Cornflower Blue Sapphire or Kashmir Sapphire. A unique
type of sapphire, known as color changing Sapphire, shows various color
patterns depending upon the lightening. In natural light, it is blue, but in
artificial light, it is violet. Pink and yellow Sapphire has recently become
very popular, and is often used in jewelry.
Sapphire mainly consists of minor inclusions of
minute slender Rutile needles. These inclusions decrease the transparency and
clearness of a stone and are called as silk.
In dense and parallel groupings, the inclusions can actually improve by
allowing polished Sapphires to exhibit asterism (a prominent star like pattern).
Sapphire gems displaying asterism are called as ‘Star Sapphires’, and these are
highly expensive.
It is pleochroic, displays an intense and lighter color
when viewed at different angles. Some pleochroic Sapphire is purple when viewed
at one angle, and blue at a different angle. Color zoning, which is created
from growth layers that build up at the time of the formation of the stone, may
also be present in certain Sapphires. Color zoning is certainly responsible for
darker and lighter colors of Sapphire. Many Sapphire gemstones are even
multicolored such as pink, blue and purple.
Machining sapphire is very complex and difficult process. Its
machining requires special types of tools and techniques. An ideal machining
procedure is possible only if favorable conditions are provided. Diamond
tooling method is highly used in machining sapphire. It is a tough and durable
element and only natural gemstone harder
than Diamond. Inspite of this, Sapphire is still subject to fracture and
chipping if handled roughly.
