Book Appointment
Marylebone, London

A guide to ethical gemstones

loose sapphires

Table of contents

Primary Item (H2)

Beautiful, colourful, precious gemstones. But what exactly are they, where do they come from, and what do you need to consider when looking at gemstone engagement rings? Read on to learn all about these wonderful jewels, how we source these ethically, and and how to look after them.

What is a gemstone?

A gemstone is a decorative stone used in jewellery which is usually cut and/or polished to enhance its appearance. 

Found in a wide variety of colours, shapes, and sizes, there are more than 300 recognised varieties of gemstones, each one with its own unique appearance and properties. 

The use of gemstones dates back thousands of years and across many cultures, and a wide range of beliefs and traditions have evolved around them, though they are most often used to symbolise love, wealth, and status. 

How are gemstones formed?

Despite the huge variety of gemstones that exist, most of them are formed deep within the Earth from minerals that have been exposed to high temperatures and pressure due to geological processes such as volcanic activity. Many are formed from silica-rich solutions driven through cracks and fissures in rocks, where they gradually solidify over time. Some gemstones are even created from meteorites impacting the Earth, causing the high-temperature and high-pressure melting of minerals.

The exact process of formation and the type of minerals present determine each gemstone's unique physical and optical properties, while certain impurities or trace elements, such as chromium, iron, manganese, magnesium, and vanadium, determine the colour of gemstones.

Diamond is unique in being formed from carbon, while pearls and amber are unusual since they are made from organic materials. Pearls are formed inside oysters and mussels in response to an irritant entering the mollusc's shell. To protect itself from the irritant, the mollusc secretes 'nacre', which covers the irritant and gradually builds up over time to form a pearl. Amber, on the other hand, is formed from fossilised tree sap.

The Mohs scale of mineral hardness

Gemstone hardness is measured using the Mohs scale, with 10 being at the top of the scale (hardest) and 1 being at the bottom (softest).

The hardness of a particular gemstone is an important consideration when choosing a gemstone. You need to know whether the gemstone you choose will stand up to the level of wear and tear it is likely to be exposed to. Earrings and necklaces do not tend to experience much wear and tear, so softer gemstones should be fine in this type of jewellery. Rings however are subjected to greater wear and tear, so harder gemstones are advisable. And engagement rings, which tend to be worn every day for many years should only be set with the hardest varieties of gemstones.

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.


Cushion cut 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.


Round cut 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.


Rectangular octagonal cut 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.


Oval cut 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.


Two round brilliant cut diamonds
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.


Rectangular octagonal cut 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.


Rhodolite cushion cut 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.


Natural blue iridescent 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.


String of pearls
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.


Square cut 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.


Oval cut 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.


Pear cut blue 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.


Cushion cut 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.


Rectangular octagonal cut 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.


Oval cut blue 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.


Oval cut 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.

What to know when purchasing a gemstone

Use the 4Cs

Like diamonds, the value of coloured gemstones is determined by the 4Cs of carat weight, colour, clarity and cut. Unlike diamonds, however, there are no universally accepted grades for colour, clarity or cut for coloured gemstones. Hence, as a buyer, it is up to you to assess these for yourself and seek a reputable jeweller's advice.

Coloured gemstones are rarely certified

Unlike diamonds, which are typically supplied with a gemological report or certificate confirming the stone's size (carat weight) and quality (colour, clarity, cut), gemstones rarely come with any comparable certification.

Only some very high-value coloured gemstones are supplied with gemological reports, and even these will typically only confirm the gemstone variety and carat weight and give an overall description of the stone. They will also comment on whether the stone has been treated (see more below). None of the more reputable gemological certificates provides colour or clarity grades. 

Consider gemstone hardness

As discussed above, gemstone hardness is measured using the Mohs scale, from 1 (softest) to 10 (hardest). The hardness of a particular gemstone is an important consideration when choosing a gemstone. You need to know whether the gemstone you choose will stand up to the level of wear and tear it is likely to be exposed to. Engagement rings, which tend to be worn every day for many years are best set with the hardest varieties of gemstones, such as diamonds, sapphires and rubies.

Look out for treatments

Many gemstones are treated to enhance their colour and clarity. Gemstones that naturally have superior colour and clarity, without treatment, are of higher value than those that achieve the same appearance through treatment. For this reason, treatments should always be disclosed.

There are a couple of exceptions to this 'rule'. Firstly, unless you are told a sapphire or ruby is unheated, you should assume that it has been heat-treated. This improves colour and clarity, has been performed for hundreds of years, and is known to be permanent and stable. About 80% of gem-quality sapphires and rubies are heated, and most unheated stones will be supplied with a gemological report confirming this.

The second exception is the oiling of emeralds, which also improved their colour and clarity, but is a temporary treatment. An emerald will need to be re-oiled to retain its optimal appearance. While some emeralds will only have been exposed to a minimal amount of oil from the stone cutters wheel, others will be heavily oiled. It is, therefore, important to understand the degree of oiling that an emerald has been exposed to.

However, there are other non-standard treatments of sapphires and rubies (glass filling, for example) and emeralds (resin treatments, for example) that should always be declared.

Synthetic gemstones

Just as it is now possible to create gem-quality lab grown diamonds, other coloured gemstones can also be made, including lab grown sapphires, rubies, emeralds and Alexandrites. These are real gemstones with the same properties and appearance as natural gemstones but are available at a lower cost than their natural counterparts. While there is absolutely nothing wrong with buying a lab grown gemstone, as with treatments, the lab grown status should always be declared. 

Ethical sourcing

Just as diamonds have been associated with human exploitation and conflict, unfortunately, colour gemstone production can involve child labour, exploitative working practices, dangerous working conditions and the destruction of local flora and fauna. So, if you want to ensure that your gemstone is contaminated by human suffering and environmental damage, it is vital to know where it has come from and how it was produced. Note that traceability is critical – unless you know where a gemstone has come from, it is impossible to know whether it was ethically produced.

Our sources of ethical gemstones

Ingle & Rhode was launched to offer our customers the finest jewellery produced from ethically-sourced precious gems and metals. To do this, we have established relationships with selected ethical producers worldwide.

Gemstone varietyIngle & Rhode's ethical gemstone sources
AmethystSri Lanka
CitrineSri Lanka
GarnetSri Lanka
PeridotSri Lanka
SapphireSri Lanka
SpinelSri Lanka
TopazSri Lanka
TourmalineSri Lanka
Country of origin of Ingle & Rhode's ethically-sourced gemstones

How to care for gemstones

All gemstones should be treated with reasonable care. Even diamonds, famously the hardest known material on Earth, can be chipped. Other gemstones can be chipped more easily than diamonds and can also be scratched. 

It is sensible to remove gemstone jewellery before you participate in sports or other activities which might increase the likelihood of you damaging it. Removing gemstone jewellery before you go to sleep at night and before taking a shower or bath is also good practice.

When you're not wearing your gemstone jewellery, store it safely in your jewellery box.

Most gemstones can be gently cleaned with a little warm water and a drop of washing-up detergent using a very soft brush (a soft child's toothbrush is ideal), but avoid exposing gemstones to harsh chemicals, solvents or cleaning products.

Pearls are particularly soft and should only be wiped with a damp cloth. Likewise, do not soak emeralds or use too much detergent, as this may remove oils from the stone. 


What is the most popular gemstone?

Diamonds are the most popular gemstones, followed by sapphires, with emeralds taking third place.

What is the most valuable gemstone?

The most valuable gemstone in the world is the Koh-I-Noor (The Mountain of Light), a colourless diamond weighing 105.6 carats and part of the British Crown Jewels. It is considered priceless. 

What is the best gemstone for an engagement ring?

Being the hardest gemstone (indeed the hardest known anything!), diamond is particularly well suited to withstanding the daily wear and tear that engagement rings are exposed to over many years. That said, if you're looking for something a little different, sapphires and rubies are also very hard gemstones (but not as hard as diamonds).


The use of decorative use of gemstones dates back thousands of years, and there are more than 300 recognised varieties, each one with its own unique appearance and properties.

Traditionally, diamonds, rubies, sapphires, and emeralds were considered precious gemstones, with all other gems being considered semi-precious. However, this distinction is used increasingly rarely in the jewellery industry as some other gem varieties can also command very high prices.

When choosing a gemstone, it is essential to consider the size, colour, clarity and cut of the stone; to confirm whether or not it is natural and whether or not it has been treated; and to ensure that it is traceable and ethically sourced.

Finally, all gemstones should be treated with reasonable care to avoid damaging them. This includes being careful about how you clean them.

David Rhode
Together with Tim Ingle, David created Ingle & Rhode to offer a better alternative to the traditional luxury brands. Since 2007, we’ve provided our customers with genuinely ethical engagement rings, wedding rings and fine jewellery – free from conflict diamonds, dirty gold and child labour. With more than 16 years experience in the jewellery industry, David has deep expertise in diamonds, gemstones and jewellery design and manufacturing.