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the mixed cut. Spinel is also mistaken for garnet or jacinth due to colour, but it has a lower hardness.
Reputed Spinels
Most
of the spinels were first taken to be rubies and were latterly
recognized as spinels: (1) Rudolph IPs ruby. It was 100 carats in
weight and is now said to be a spinel. (2) The ruby set in the crown of
His Imperial Majesty is now considered to be a spinel. In the
exhibition of 1862, two large spinels were shown. They weighed 197 and
respectively
after cutting. The French crown jewels also contained a number of
spinel rubies, as for instance 56| carats and blue spinel
Chapter XIV CHRYSOBERYL
Introduction and Physical Properties
CHRYSOBERYL
means yellow beryl and it is an ancient name. Its variety, cat's eye,
was well-known and appreciated from ancient times. It was known as '
Vaidooryam' in India. This mineral was recognized before the discovery
of the element beryllium, which is an essential constituent of the
mineral. It crystallizes in the orthorhombic system and forms
heart-shaped and pseudo-hexagonal twins. These crystals are grown
together with interpenetration. The mineral has a pinacoidal cleavage
and conchoidal fracture. Hardness =
Colour
varies from pale yellow, brown or green. Lustre: Vitreous and silky in
cat's eye. Transparent to translucent. Mean refractive index =
119
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