|Less than one in 10,000 gem-quality diamonds is classified as ‘fancy-coloured’. The various colours are formed under unique conditions involving specific trace elements, radiation and/or plastic deformation of the crystal structure.|
Monday, 22 October 2018
Sunday, 21 October 2018
|Color change garnets are due in part to varying concentrations of vanadium and chromium. The blue-green to purple color change garnets have relatively high concentrations of vanadium and low concentrations of chromium.|
Very fine, gem quality blue garnets over 10 carats are scarce and valuable.
Friday, 19 October 2018
|Ammolite is an opal-like organic gemstone found primarily along the eastern slopes of the Rocky Mountains of North America. It is made of the fossilized shells of ammonites, which in turn are composed primarily of aragonite, the same mineral that makes up nacreous pearls. |
It is one of the few biogenic gemstones; others include amber, pearl and coral.
|An iridescent opal-like play of colour is shown in fine examples, mostly in shades of green and red although all the spectral colors are possible. |
Iridescence is due to the microstructure of the aragonite: unlike most other gems, whose colors come from light absorption, the iridescent color of ammolite comes from interference with the light that rebounds from stacked layers of thin platelets that make up the aragonite.
|The thicker the layers, the more reds and greens are produced; the thinner the layers, the more blues and violets.|
Tuesday, 16 October 2018
|Van Cleef & Arpels|
Jacob & Co
Monday, 15 October 2018
Sunday, 14 October 2018
|It all started with the marriage of Estelle Arpels and Alfred van Cleef in 1895. In 1906 they started to work under one name: Van Cleef & Arpels. Today it is a household name for the finest gems on earth.|