A Quick Guide to Emeralds,
Rubies and Sapphires

Gemfields is the world’s leading supplier of responsibly mined coloured gemstones. We specialise in Zambian emerald and Mozambican rubies. At Gemfields we have a team of experts who understand the very unique geology.

Our aim is to give confidence and to demonstrate that responsibly-mined, coloured gemstones can be consistently supplied and relied upon.

Emerald

Ruby

Sapphire

Origin of the name
It comes from the ancient Greek word for green, “smaragdus”.
In Sanskrit, ruby is "ratnaraj", meaning the king of gems.
Its name comes from the Greek word "sappheiros", which probably referred to lapis lazuli.
Mineral Family
Beryl
Corundum
Corundum
Chemical composition
Be3Al2Si6O18
Al2O3
Al2O3
Origins & geological age
Zambia (500 million years old), Colombia (50 million years old), Brazil, Afghanistan, Russia, Zimbabwe, Ethiopia
East Africa (Mozambique, Madagascar, Kenya, Tanzania), the Himalaya, Southeast Asia (Myanmar, Thailand and Vietnam) and Tajikistan
Thailand, Madagascar, Tanzania, Sri Lanka, Myanmar, Australia, Kenya
Main Colour
Green
Red
Blue
Modifying Hues
Yellowish green to bluish green
Orangy red to purplish red
Greenish blue to violetish blue
Mohs Scale of Hardness
7.5 to 8
7.5 to 8
9
Value factors
A pure vivid green colour, few or no visible inclusions, sizes above 20ct
A pure vivid red colour (also called "pigeon's blood" in the trade), no visible inclusions, sizes above 10ct
A deep intense velvety blue colour (also called "Royal Blue" in the trade), no visible inclusions or colour zoning, sizes above 30ct
Unusual characteristics that add value…
Inclusions whose appearance resembles a "jardin"; transparency in supply chain, thanks to DNA technology (link to Gübelin and Gemfields paternity testing web page)
Silk inclusions that produce a star effect, or just enough delicate intersecting needles to make the ruby "glow" under natural light
Silk inclusions that produce a star effect, or just enough delicate intersecting needles to make the sapphire "glow" under natural light
COMMON TREATMENTS
Traditionally, oil is applied to emeralds for improving colour and transparency; modern treatments include fracture filling with resins and wax. Never heat treated.
Heat treatment is traditionally applied to rubies to improve colour and remove visible inclusions; sometimes heat treatment is coupled with fillers such as glass or borax to fill fractures and make them less visible.
Heat treatment is traditionally applied to sapphires to improve colour and remove visible inclusions; sometimes heat treatment is used to add fillers such as beryllium or titanium to fill fractures and make them less visible.
Birth & anniversary stones…
Birthstone for the month of May; gemstone for 20th and 35th anniversaries
Birthstone for the month of July; gemstone for 15th and 40th anniversaries
Birthstone for the month of September; gemstone for 5th and 45th anniversaries
The colour symbolises...
Green is for birth, hope, good health and good vision.
Red is for intense emotions, love and passion.
Blue is for wisdom, virtue, good fortune, and in an engagement ring it symbolises faithfulness and sincerity, too.
Auction world record…
The 2017 sales price for the Rockefeller Emerald, a Harry Winston ring with an octagonal cut Colombian emerald of 18.04ct, set a new world record of $5,511,500 (or $305,516 per carat).
The 2015 sales price for the Sunrise Ruby, a Cartier ring with a cushion cut Burmese ruby of 25.59ct, set a new world record of $30,335,698 (or $1,185,451.27 per carat).
The 2015 sales price for the Jewel of Kashmir, a ring with an octagonal cut Kashmir sapphire of 27.68ct, set a new world record of $6,702,564 (or $242,145 per carat).
Fascinating fact…
The first known emerald mines were in Egypt, dating from around 330 BC into the 1700s. Cleopatra was known to have a passion for emeralds, and used them in her royal adornments.
Rubies are one of the most historically significant colored stones; they are mentioned four times in the Bible, in association with attributes like beauty and wisdom.
Sapphires appeared in the world’s most famous engagement ring: the one that was worn by both Princess Diana and Kate Middleton.