Short answer: ruby is the July birthstone. It is red corundum, the same mineral as sapphire, colored by chromium. At 9 on the Mohs scale it is second only to diamond in hardness among popular gems, which makes it excellent for everyday rings. Myanmar has produced some of the most sought-after rubies for more than five centuries. Most rubies are heat treated, which is stable and accepted in the trade.
What is the July birthstone?
July has one birthstone on the modern United States list: ruby. It is also the gem traditionally given for the 15th and 40th wedding anniversaries. In ancient India, ruby was called the "king of precious stones" for its rarity, hardness, beauty and the powers it was said to hold.
What is ruby?
Ruby is corundum, crystalline aluminum oxide. Pure corundum is colorless; red corundum is ruby, and corundum of every other color is sapphire, the September birthstone. The word ruby comes from ruber, Latin for red.
Ruby's color comes from chromium. When a chromium atom replaces an occasional aluminum atom, it absorbs yellow-green light, leaving red. It also makes ruby fluoresce, giving off extra red light, which adds to its glow. Ruby has no true cleavage and a specific gravity of about 4, making it noticeably heavy for its size.
What color is the July birthstone?
Red, from orangy red to strongly purplish red. The brightest and most valuable shade, called "pigeon blood", commands a large premium. Many rubies from Mogok, Myanmar, are vibrant reds softened by light-scattering inclusions and a glowing red fluorescence.
Rubies that are not rubies
Some famous historical "rubies" are actually spinel, a different mineral. The Black Prince's Ruby in the British Imperial State Crown is one. Red spinels were once called "Balas rubies". Spinel is now an August birthstone in its own right.
Where do rubies come from?
- Myanmar: the Mogok area has produced some of the world's most sought-after rubies for more than five centuries, in a landscape of weathered marble and ancient Buddhist temples.
- Vietnam has been an important source since the late 20th century, from the Luc Yen region in the north, which produces red to purplish red rubies, and the Quy Chau district farther south.
- Mozambique is an important newer source, with prolific mines at Montepuez whose rubies have been compared to those of Mogok.
- Thailand and Cambodia: for many years in the late 1900s, deposits along their border were the major source of rubies on the market.
Afghanistan, Tajikistan, Pakistan, Sri Lanka, Kenya, Tanzania and Madagascar also produce rubies.
What does the July birthstone mean?
Long associated with blood and the life force, ruby was a symbol of power and youthful energy in Indian jewelry. Some believed it could predict misfortune or danger, Burmese warriors believed it made them invincible in battle, and medieval Europeans believed it brought wisdom, wealth and success in love.
These are traditions and beliefs, part of the stone's long history, not properties of the gem.
Is ruby treated?
Usually. Almost all rubies are treated in some form, and heat treatment is the most common. Heating removes purplish color, leaving a purer red, and can dissolve "silk", fine needle-like inclusions that make a stone look lighter and less transparent. The trade accepts heat treatment because it is stable in normal wear.
Other treatments are less benign. Rubies may be treated by lattice diffusion or dyed, and in lower-quality material, fractures and cavities may be filled with glass so the stone looks more transparent. Some of these treatments make a ruby more vulnerable to damage. In the United States, the Federal Trade Commission requires disclosure of treatments that affect a gem's value, so always ask.
Lab-grown ruby
Ruby was among the first gems made in a laboratory. In 1837 the chemist Marc Antoine Gaudin made synthetic rubies by fusing potash alum at high temperature with a little chromium. Lab-grown rubies have the same chemistry and hardness as natural ruby and should be sold as synthetic. Gemologists use natural inclusions, such as rutile needles, to help tell natural rubies from synthetics.
Ruby in zoisite, fuchsite and kyanite
Many crystal shops sell rocks that contain ruby rather than faceted gems.
- Ruby in zoisite, also called anyolite or ruby zoisite, is a metamorphic rock of green zoisite, black pargasite and ruby, first found at the Mundarara Mine near Longido, Tanzania, in 1954. Its name comes from the Maasai word anyoli, "green". The contrasting colors make it popular for carvings and spheres.
- Ruby in fuchsite and ruby in kyanite are other ruby-bearing rocks, pairing red ruby with green, chrome-bearing fuchsite mica or with blue kyanite.
They are sold as decorative stones, carvings and tumbles rather than as faceted gems.
How do you care for ruby?
- Clean it with warm, soapy water and a soft brush, which is safe in most cases.
- Ultrasonic and steam cleaners are usually safe for untreated, heat-treated and lattice diffusion-treated rubies.
- Glass-filled or dyed rubies should only be cleaned with a damp cloth.
- Store it apart from softer gems, which ruby can scratch.
Browse crystals and minerals at Digital Towns Market
Digital Towns Market
Ruby and ruby-bearing stones in stock
Frequently asked questions
What is the July birthstone?
Ruby, the red variety of the mineral corundum.
Are ruby and sapphire the same stone?
They are the same mineral, corundum. Red corundum is ruby; every other color is sapphire.
What is pigeon blood ruby?
"Pigeon blood" is the trade name for the brightest and most valuable shade of red in ruby. It commands a large premium.
Is ruby good for an everyday ring?
Yes. At 9 on the Mohs scale, with no true cleavage, ruby is one of the most durable gems for rings worn every day.
Are most rubies heat treated?
Yes. Almost all rubies are treated in some way, most often by heating, which is stable and accepted in the trade. Glass filling and dyeing are less durable and should always be disclosed.
What is ruby zoisite?
Ruby zoisite, or anyolite, is a Tanzanian rock of green zoisite, black pargasite and red ruby, often carved into spheres and decorative objects.
Sources
- GIA, July Birthstone: https://www.gia.edu/birthstones/july-birthstones
- GIA, Ruby: https://www.gia.edu/ruby
- Wikipedia, Ruby: https://en.wikipedia.org/wiki/Ruby
- Wikipedia, Anyolite: https://en.wikipedia.org/wiki/Anyolite