Gemstones Buying Guide Series No.5

Gemstones Buying Guide Series No.5

Published only on Monday’s.  Extracted from Gemstone Buying Guide by Renee Newman GG

 

Colored Gem Price Factors :

Following factors can affect the prices of coloured gemstones:

-          Color

-          Clarity

-          Transparency

-          Shape

-          Cutting Style

-          Cut Quality

-          Carat Weight or stone size

-          Treatment status

-          Place of Origin

-          Distinctness of phenomena

 

Place of origin may refer to the country, area, or mine where a gem was mined.  In most cases the source if colored gems does not matter – it’e the quality that counts.  However, for gems such as ruby, sapphire and emerald, origin can affect the price, provided the stone has a high quality and is accompanies by a lab report indicating a desired source.

 

Distinctness of Phenomena: Phenomena are unusual optical effects such as:

-          Chatoyancy (cat-eye): a band of reflected light in cabochons .  It occurs when a strong light strikes needle-like inclusions or hollow tubes that are parallel within the stone.  A cat’s eye effect may be seen on some chrysoberyl, emerald, aquamarine, apatite, quartz and tourmaline

-          Asterism (star): bands of reflected light crossing each other in the center to form a star with four, six or twelve rays

-          Adularescence: a floating, shifting light effect caused by structural unevenness in moonstone which scatters the light.  On some high dome moonstones, it creates a cat’s eye effect.

-          Aventursence: a glittery, sparkling effect caused by light reflecting off of minute platelike inclusions.  In sunstone, the inclusions are usually platelets of copper or hematite, ad in aventurine quartz they’re a type of green mica

-          Labradorescence:  a flesh of color(s) in labradorite or spectrolite seen at certain viewing angles.  It’s caused by the interference of light through the layered structure of labradorite

-          Color change: sometimes called the alexandrite effect.  A change of color that occurs when the light source is changed.

-          Play of colors:  a display of shifting colors in opal caused by clusters if microscopic silica spheres of uniform size, which break up the light into spectral colors

-          Orient: pearl iridescence. It results from the interference that occurs as light passes through layers of nacre.  Orient may be a subtle combination of rainbow-like colours or of pink, blue, silver and sometimes green.

Iridescence: a play of lustrous changing colors caused by the interference of light