2. Coral is considered as an auspicious gem by
many Indians and astrologically representing the
planet mars.
Delicate, soft and chemically reactive.
Organic origin and constitutes a skeleton from
which certain tiny living organisms or polyps
protrude.
3. Coral is an invertebrate animal belonging to the
phylum coelenterate (cnidaria).
Coral animals are marine mostly colonial, polypoid
cnidaria, looking like miniature sea anemones
(sea flowers).
They live in a secreted skeleton of their own.
Growth of coral is restricted to warm water of sea.
Their calcareous or horney skeleton is also
commonly known as coral.
4. Immobile skeleton being to grow over substratum
such as a rock boulder.
Consists of longitudinal ridges filled with
cryptocrystalline calcite.
Thickness of skeleton is about 4 cm at the base
and grows to a height of about 25cm.
coral colony appears like a leafless blooming bush
with myriads of white flowers.
5. Of the several types of corals only certain species
are used in the gem industry and these are
referred to as many as 20 species, of which, the
most sought after species is corallum rubrum
whose colour is red to white.
skeleton is more solid.
Black coloured coral is rich in organic matter.
6. Objects carved from red, pink, white and black
coral skeleton take glassy polished and appear
very elegant.
Coral was a popular gem in ancient times.
Fashion of wearing this gem has cropped up once
again in the modern times.
7. Chemical composition=CaCO3 (calcite)
Specific gravity= 2.6-2.7
Hardness=3.5
Colour=red, pink, white, greyish blue, black etc.
colour may often may vary from core to the border
of coral stock.
Wherein the central axis may be white and the
outer portion being pink or vice-versa.
8. The cause of colour appears to be due to organic
matter present in it.
Refractive index does not have meaning in coral,
as it is made up of extremely birefringent.
Cryptocrystalline particles of calcite.
As it is made up of calcite, it rigorously reacts in
dilute HCl. But black coral is rich in organic matter.
It does not react with HCl so rigorously.
9. Several types of simulants of coral have been
manufactured.
Plastics and glasses are commonly used as
imitations.
Mixtures of several types of materials are
manufactured to counterfeit coral.
Generally, the corals fail to react with HCl
10. In India reefs are located in the Gulf of Kuch, Gulf
of Mannar, Lakshadweep and Andaman and
Nicobar Islands.
A vast majority of precious coral, however, is
imported into Indian from Italy and other countries.
