Chrysoberyl

Chrysoberyl, traditionally considered as ‘semi-precious, is actually the name of a gem species* that has three important gem varieties.  When the term chrysoberyl is used alone it usually refers to the lesser-known greenish yellow variety.  The other two gem varieties are chrysoberyl cat’s eye** and alexandrite. 

Chrysoberyl cat’s eye is usually yellow to yellowish-green and displays a chatoyancy (cat’s eye) effect. Alexandrite displays a colour change effect appearing red to purplish-red in incandescent light and green in daylight.  Chrysoberyls form in pegmatites or high pressure metamorphic rock.  Rough chrysoberyl often presents as tabular or twinned crystals.

Where can you find the chrysoberyl you need ?

Pierres de Charme carries a vast selection of fine quality yellow chrysoberyl, cat’s eye, and alexandrite.  Our collection of well-cut stones includes many different shapes and sizes ranging from melee to exceptional stones.  

• Yellow and yellowish green chrysoberyl is the most common variety and has been used in jewellery since antiquity.  Gemmologists can easily identify this material by its diagnostic absorption spectrum caused by iron (Fe) in its structure.  It can be found in Brazil, Sri Lanka, Madagascar, Myanmar, and Zimbabwe.  The gem’s size, colour saturation, and clarity will affect the value.  The name comes from the Greek “khrusos beryllos” meaning golden beryl.

• Cat’s eye chrysoberyl owes its optical phenomenon to the presence of numerous fine needle-like or tubular inclusions.  Light is reflected off these inclusions creating a fine bright line that appears to float on the surface of the stone.  This material must be fashioned as a cabochon in order to display the effect.  Its yellow and golden hues are the result of small amounts of iron present in its structure and cat’s eye will show the same diagnostic spectrum as yellow chrysoberyl.  Important deposits are found in Brazil, Myanmar, Sri Lanka, India, and Zimbabwe.  The gem’s size, colour, and quality of the optical effect will have an impact on value.  ‘Milk and Honey’ is a term used to describe the contrast between the light golden body colour and the luminous white cat’s eye effect of the finest quality cat’s eye chrysoberyls. 

• Alexandrite is the chrysoberyl variety that displays a colour change effect.  This optical phenomenon is caused by the presence of chromium (Cr) in the gem’s structure which, depending on the light source (daylight or incandescent), absorbs visible light producing different colours. Alexandrite is the most sought after and expensive chrysoberyl variety. Very rare specimens of alexandrite can display both a colour change effect and a cat’s eye effect.

Gemmologists can easily identify alexandrite by its diagnostic chromium (Cr) spectrum.  Synthetic alexandrite is common on the market and gemmologists rely on the presence of certain inclusions in order to distinguish natural gems from synthetic versions.  Discovered in 1830 in Russia’s Ural Mountains, alexandrite was named in honour of the young Tsar Alexander II.  The green and red colours shown by alexandrite were the official colours of Imperial Russia and the gem quickly became a favourite in its homeland.  Today, the main source of gem quality alexandrite is Brazil.  The gem’s size, colour saturation, clarity, and intensity of the colour change effect will all have an impact on value.  Most alexandrites on the market are under 1.00 carat and larger sizes can sell at a significant premium.  Alexandrite is the birthstone for the month of June and the gemstone for the 55^th wedding anniversary.

Chrysoberyl Fact Sheet

All chrysoberyl varieties display a bright vitreous lustre and have a hardness of 8.5 on the Mohs scale.  Their excellent toughness, resistance, and stability make them suitable for all styles of jewellery. 

Chrysoberyl varieties do not respond well to heat treatment and are not routinely treated.  When surface reaching fractures are present a fracture filling treatment can be performed to enhance the gem’s appearance. This treatment can be detected using a microscope.

Chrysoberyl in Jewellery

Chrysoberyl’s excellent hardness, stability, and toughness have made it very popular with jewellers and consumers alike.  It is suitable for all types of jewellery and will retain its beauty over time.  Cat’s eye and alexandrite are particularly popular with gem enthusiasts and collectors.

*In gemmology, as in nature, a species refers to a group with related members who share common features. In gemmology, the varieties or members of a species, share a common chemical composition of atoms organized in identical repeating patterns. In most cases the individual varieties are differentiated by the presence of small amounts of a chemical element that causes the particular colours associated with the different varieties.

**When used alone, the name ‘cat’s eye’ automatically implies that the stone is a chrysoberyl. Other gemstones can show a cat’s eye effect and they should be named using the mineral name preceded by the term ‘cat’s eye’ for example: cat’s eye tourmaline.

Chr-1. In Cours de base en gemmologie Gem-A. London, 2010

Alexandrite History and Lore. (n.d.). Retrieved August 06, 2016, from http://www.gia.edu/alexandrite-history-lore

Gem property Chart A [Chart]. (n.d.). In Gemological Institute of America (GIA). 1992