|
|
name:
|
Blue Tourmaline
|
| gemstone variety:
|
Tourmaline
|
| trade name 1:
|
Blue Tourmaline
|
| trade name 2:
|
Indigolith
|
| trade name 3:
|
Indigolite
|
| basic colour:
|
blue
|
|
|
Colour :
|
all shades from a greenish-blue to plain dark blue
|
Quality :
|
the more desirable colour is a plain Sapphire blue
colour rather than a black blue colour. The intensity should
be an optimum, not a maximum. Facetted blue Tourmalines
should have no visible inclusions and balanced proportions
in the cut.
|
History :
|
The name tourmaline is derived from the Singhalese
word "turamali" meaning gemstone. 'Indigolith' is named
because of its indigo-blue colour, which is very desirable
for jewellery.
|
Curiosities / Saga :
|
|
Countrys of Origin :
|
Brazil, Namibia, Tanzania, Mozambique, Madagascar and
Afghanistan
|
Birthstone :
|
October - Tourmaline
|
Hardness :
|
7.5
|
Treatment :
|
sometimes heat-treated
|
Size :
|
normally from 0.50 to 10.00 carats
|
Specific gravity :
|
3.10 - 3.20
|
Chemical Composition Formula :
|
Na(Li,Al,Fe)3 Al6 (BO3)3 Si6O18 (OH)3F
|
Chemical Composition Name :
|
Hydrous and fluor bearing sodium-l ithium- aluminium-
iron- boronsilicate
|
Crystal system :
|
trigonal
|
Light refraction :
|
1.610 - 1.640
|
Double refraction :
|
0.016 - 0.022
|
|
|
