Different types of gemstones
With there being more than 300 varieties of gemstones, we can't cover all of them in this article, but here's a quick summary of our top 16 gemstones, which between them account for more than 95% of all gemstone sales by value.
Alexandrite
Cushion cut Alexandrite
Alexandrite is a rare variety of the mineral chrysoberyl (a cousin of emerald and aquamarine) that is notable for its colour-change properties. It is typically green in daylight and red or pinkish-red in incandescent light. The rarity and beauty of Alexandrite make it a highly sought-after and precious gemstone. The finest Alexandrite can often cost considerably more than diamonds of comparable size. Scoring 8.5 on the Mohs scale, Alexandrite is well suited for use in engagement rings.
Amethyst
Round cut amethyst
Amethysts are a variety of quartz and are known for their purple colour. They are one of the more affordable gemstones but relatively soft (7 on the Mohs scale), meaning they are not best suited for use in engagement rings.
Aquamarine
Rectangular octagonal cut aquamarine
Aquamarine is a variety of beryl (like emerald) and is known for its bluish-green colour. Aquamarines are widely used in jewellery, make a wonderful choice centrepiece in bespoke engagement rings, and tend to be one of the more affordable gemstones. They score between 7.5 and 8 on the Mohs scale, meaning they stand up well to wear and tear.
Citrine
Oval cut citrine
Citrine is a yellow-to-orange variety of quartz. Although it can be formed through natural processes, it is often produced commercially by heating amethyst or other types of quartz. Like amethyst, citrine scores 7 on the Mohs scale, meaning it is not well suited for use in engagement rings.
Diamond
Two round brilliant cut diamonds
Diamonds are the most well-known and popular gemstone, prized for their transparency, fire and brilliance. Diamonds are extremely hard, scoring 10 on the Mohs scale, making diamond engagement rings an ideal choice for those wanting to propose to their partner. Most often seen in jewellery as a white gem, diamonds are also found in various (extremely rare) "fancy colours", including yellow, pink and blue.
Emerald
Rectangular octagonal cut emerald
Emeralds are a precious variety of the mineral beryl and are prized for their deep green colour. Although widely used in fine jewellery, emeralds are notably softer than diamonds, sapphires and rubies, scoring 7.5 to 8 on the Mohs scale. Although emerald engagement rings remain extremely popular, owners of these beautiful rings need to take extra care not to damage the gemstone through wear and tear.
Garnet
Rhodolite cushion cut garnet
Garnets are most often thought of as red gemstones, similar in appearance to rubies, though garnets are found in a range of different colours. They are a group of different gemstones with the same crystal structure but vary in chemical composition. For example, almandine garnets are formed from iron-rich magnesium silicates, while pyrope garnets are formed from magnesium-rich iron silicates. Scoring 6.5 to 7 on the Mohs scale, garnets are not well suited for use in engagement rings.
Opal
Natural blue iridescent opal
Opals are unique gemstones, prized for their iridescent "play of color". Formed from hydrated silica, their water content is usually between 6% and 10% but can be as high as 20%. Scoring just 5 to 6.5 on the Mohs scale, opals are not well suited for use in engagement rings.
Pearl
String of pearls
Pearls come in a variety of colours, including white, black, and pink, and their value depends on whether they are natural or farmed, and factors such as their size, shape, lustre, and surface quality. Scoring just 2.5 on the Mohs scale, pearls are very soft gems, not well suited for use in engagement rings.
Peridot
Square cut peridot
Peridot is a green variety of the mineral olivine known for its bright green colour. Indeed, it is one of the few gemstones that occur in only one colour. Scoring 6.5 to 7 on the Mohs scale, garnets are not well suited for use in engagement rings.
Ruby
Oval cut ruby
Rubies are a red variety of the mineral corundum and are one of the most valuable gemstones in the world. Like sapphires, rubies are known for their durability, scoring 9 on the Mohs scale of hardness, meaning that ruby engagement rings are well able to stand up to wear and tear.
Sapphire
Pear cut blue sapphire
Sapphires are a precious variety of the mineral corundum and are known for their deep blue colour, though they are also found in a wide range of other colours, including pink, yellow, green, orange and purple. Sapphires have been used in jewellery for many hundreds of years and are very hard gemstones, scoring 9 on the Mohs scale, making sapphire engagement rings an extremely popular choice for those looking for something a little bit different.
Spinel
Cushion cut spinel
Spinel is a group of related minerals formed from magnesium aluminium oxide and found in various colours, including red, blue, green, pink, and purple. Spinel has a long history of use in jewellery, especially as a lower-cost substitute for ruby and sapphire. And scoring 8 on the Mohs scale, spinels are hard enough for use in bespoke engagement rings.
Tanzanite
Rectangular octagonal cut Tanzanite
Tanzanites are blue-violet gemstones that were only discovered as recently as 1967. A variety of the mineral zoisite, Tanzanite is only found in the Mererani Hills of Tanzania colour. A relatively soft stone, scoring between 6 and 7 on the Mohs scale, Tanzanite is highly prized for its colour, clarity and scarcity.
Topaz
Oval cut blue topaz
Topaz is commonly found in shades of yellow, orange, blue, and pink and is formed from aluminium and fluorine silicate. It is well suited to everyday wear with a hardness of 8 on the Mohs scale.
Tourmaline
Oval cut tourmaline
Tourmaline is a gemstone that can be found in various colours, including pink, green, blue, and black. Like topaz, it is formed from silica-rich fluids driven through cracks and fissures in the Earth's crust, where they gradually solidify over time.
One particular blue-green form of tourmaline discovered in Paraiba, Brazil, in the 1980s is particularly highly prized. Indeed high-quality Paraiba tourmaline can command up to $50,000 per carat!
Scoring between 7 and 7.5, tourmaline is used in engagement rings, but being a relatively soft stone, extra care should be taken not to damage them.
Precious stones vs semi-precious stones
Traditionally, precious gemstones were considered to be diamonds, rubies, sapphires, and emeralds. Due to their rarity and high demand in the market, they commanded higher prices than other so-called semi-precious gemstones.
However, in more recent years, the distinction between precious and semi-precious gemstones has broken down, with Alexandrites, Paraiba tourmalines, and Tanzanites, for example, regularly commanding prices equal to or more than the so-called 'precious gemstones'. As a result, increasingly fewer people within the gemstone trade refer to precious vs semi-precious gems.