A gemstone primer: An overview of gemstones fron 4Cs to Moh's Hardness Scale

Learn some informative and fun facts about gemstones to help you when considering buying that sapphire, ruby, or emerald

With so many beautiful stones coming in different colors and prices it can be a tough decision knowing what type of gemstone you want to purchase. Especially, if this is a large purchase, such as a unique custom engagement ring. Below we are going to cover some of the main qualities that give each precious colored stone its unique appeal.

Let’s Talk Sapphires

Blue is not the only color!

Sapphires are formed of a mineral called Corundum which is the crystalline form of aluminum oxide and when you think of sapphires, it is likely that you automatically think of the color blue. However, sapphires are actually found in a range of colors. Sapphires can come in almost any color, except Red. When red Corundum is found it is called Ruby. We will talk more about rubies later.

Where do they come from?

Sapphires are mined all over the world with mines found in India, Sri Lanka, Burma, Australia, Brazil, Thailand, Vietnam, Madagascar, Africa and even in the USA. Many pink and yellow sapphires are found in Madagascar with purple sapphires typically coming from Brazil.


As with diamonds, the value of a sapphire is dependent upon the 4C's of cut, clarity, color and carat. Sapphires are rare gemstones, much rarer than diamonds, and this too can add a premium to the value of a high quality sapphire. In the main, the color of the gemstone, even taking into account heat treatment to improve color, is determined by the location at which the sapphire was mined. To this end, the blue sapphires from some areas, such as Kashmir and Ceylon are considered particularly beautiful and are highly valued. High quality deep pink sapphires are also considered very valuable.


After diamonds, sapphires are amongst the hardest gemstones known to man. Corundum is 9 on the Moh's scale of hardness and this means that sapphires can be very durable hard wearing stones. As diamonds are harder than sapphires they can damage sapphires. Other sapphires and rubies can also damage sapphires, therefore as with all jewelry, it makes sense to store sapphire jewelry wrapped individually in a soft cloth.

Care and cleaning of Sapphires

The weakest point of a sapphire is at the edge or point of the cut stone where any impact could cause the sapphire to chip or shatter, for this reason, it is best to remove your sapphire jewelry when doing rough work

Sapphires can easily be scratched or scraped by the edge or point of another sapphire, as well as by rubies and diamonds. To minimize the risk of this happening, always store your sapphire jewelry wrapped individually in soft cloth.

Give your sapphire jewelry a regular clean at home in a bowl of warm water with a few drops of washing up liquid. Soak the jewelry in the water for around 30 minutes, then using a soft brush, clean around the gemstone. Once clean, removed the jewelry and dry it using a soft cloth.

Let’s Talk Rubies

Rubies are formed of a mineral called Corundum which is the crystalline form of aluminum oxide. This is the same mineral which forms sapphires, however only when the mineral is colored red, due to the presence of chromium, is it considered to be a ruby. As a result, rubies are very rare, and very valuable, gemstones.

Where Do They Come From?

Ruby mines can be found dotted around the world with the most well known mines in Burma where the most valuable, blood red rubies, have historically been found. There are also mines in Kenya which have produced some magnificent quality rubies. Ruby mines are also found in Pakistan, Sri Lanka, Thailand, Cambodia, Vietnam, Afghanistan, Mozambique and even in some areas in the United States of America.


As with diamonds and sapphires, the value of a ruby is dependent upon the 4C's of cut, clarity, color and carat. They are extremely rare, and a blood red ruby is extremely valuable.

Let’s Talk Emeralds

Emeralds are formed of a mineral called beryl. The coloring of beryl is determined by impurities with the gemstone however, only when the impurity is chromium, is the grass green beryl called emerald formed. As a result, the very rare and very valuable gemstone, emerald, is formed.

Where Do They Come From?

Emerald mines can be found around the world with the most ancient mines in Egypt where emeralds have been being mined for over 3000 years. Mines still exist in Egypt as well as other locations in Africa including South Africa, Madagascar and Zambia. Emerald mines are also found in Colombia, Brazil, Russia with some emerald deposits even found in the USA.


As you should know by now, all precious stones values are dependent upon the 4C's of cut, clarity, color and carat. Emeralds are rarer than diamonds and large, clear vivid emeralds are even rarer, making these extremely valuable gemstones. The emeralds which are an intense grass green color are the most desirable and valuable. However, emeralds of all colors ranging from a pale green to a deep rich green can also be extremely beautiful and valuable. As emeralds are type III gemstones, they naturally have many inclusions although these inclusions do not always detract from the value of an emerald.

Durability of Emeralds

Emeralds are an 8 on the Moh's scale of hardness and this means that are reasonably durable. However, the inclusions found in emeralds make them vulnerable to heat damage and extreme changes in temperature may cause them to break as can knocks or bumps. Also, given that many emeralds are oiled, exposure to harsh detergents or chemicals can dilute or dissolve the oil which has soaked into the emerald reducing their clarity and color. As diamonds, sapphires and rubies are harder than emeralds they can scratch or chip emeralds. Other emeralds can also damage emeralds, therefore as with all jewelry, it makes sense to store emerald jewelry wrapped individually in a soft cloth.

As a result of the inclusions in emeralds, whilst reasonable hard, they are vulnerable to breaking or cracking, particularly if bumped. As a result, it is best to remove your emerald jewelry when doing rough work.

Whether you decide to choose an emerald, ruby, or sapphire, all three precious stones are beautiful and rare, and will make stunning jewelry. With the right care and maintenance these stones should last through the generations.