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Black Day Special | A Guide to Black Gemstones

Black Diamond · Onyx · Black Spinel

While we often celebrate diamonds and precious gemstone as the language of love, there is nothing more important than self-love. 14 April is Black Day, also known as Black Valentine’s Day, celebrated by singles in Korea.

Black gemstones are adored for their mysterious, hypnotic, alluring aesthetic, along with the fact that the monochromatic hue makes it easy to match with any outfit. At the same time, black gemstones are believed to be some of the most effective healing stones with unique metaphysical properties and healing powers. As such, they are extensively used for astrological purposes as well as for jewellery. Common types of black-coloured gemstones include black diamonds, black pearls, onyx, spinal, black jade, obsidian, etc.

In this special Black Day edition blog entry, I will share a bit more about a few of my favourite black gemstones: black diamond, onyx and black spinel.

Black Diamond

We’ve talked plenty about white diamonds, but what about black diamonds? When black diamonds were initially discovered, they were not a popular choice, as they did not have the sparkle diamonds are most loved for.

Back when black diamonds were first discovered, they were not as popular as no one preferred a diamond that didn’t sparkle. Consumers had little interest in black diamonds until the late 20th century. Its rising popularity in recent years, however, have caused black diamonds to increase to price and value.

Comparison of Fancy White and Fancy Black Diamonds of Different Levels of Transparency and Opaqueness

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Bespoke Jewellery Order - Black Diamonds & White Diamonds Starlight Earrings,


Like other diamonds, black diamonds are made of carbon crystals, but the black colouration is a saturation of minor dark inclusions within the stone itself, which are mostly graphite but could also be sulphides, magnetite, hematite or iron-bearing materials. The other possible cause of the black hue is exposure to radiation.

Black diamonds are quite rare and are only found within the Central Africa Republic and Brazil. An important source of black diamonds, both natural and treated, is the Marange deposit in eastern Zimbabwe.


Black diamonds are opaque, with a highly lustrous and almost metallic appearance. Although black diamonds do reflect, they do not sparkle, giving a lesser brilliance than diamonds of other colours.

One thing that should be noted with the GIA’s 4Cs grading standards apply for colourless to near-colourless (D to Z colour) diamonds only. As black diamonds fall outside this colour range, their colour is evaluated based on GIA’s colour grading system for coloured diamonds.


Truly black diamonds are not very common in nature and as a result, the majority in the market are treated to achieve a uniform black colour. Many treated black diamonds are so heavily irradiated that they look black, but instead are extremely dark green.

The actual body colour of a natural black diamond may range from near-colourless to brown or olive green, depending on the concentration of the black colouration within the stone’s cleavages or fractures as a result of staining or graphitisation.

Popular cuts:

As black diamonds are so heavily included, cutting and polishing them can be difficult and they also must be set with great care. Some of the most popular cuts include round, princess, oval, pear, marquise, and heart cuts.

Maintenance and care:

As one of the hardest varieties of diamonds, black diamonds have a score of 10 on the Mohs Hardness Scale. Black diamonds should be cleaned and cared for the same way as all other diamond. Read this blog entry for detailed care and cleaning tips.


Onyx is a semi-precious gemstone whose name is derived from the ancient Greek word ὄνυξ (onux), meaning ‘fingernail’ or ‘claw’. In Greek mythology, one time when Venus, the Goddess of Love, fell asleep on the banks of the Indus River, Cupid clipped her fingernails and scattered them across the riverbank. The Greek Gods transformed the precious nails of Venus into beautiful gemstones which were later on named as ‘onyxes’.

Metaphysically, black onyx is a gemstone with healing properties and signifies protection, willpower, and calmness, while it also has the ability to protect one against evil spirits and bad temptations.

Black Onyx

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The black onyx is a type of silicate-layered chalcedony, which is a variety of quartz with a cryptocrystalline structure and is made up of natural silicon dioxide. Black onyx is formed through the sedimentation of silicon dioxide in its parent rock quartz, when quartz combines with moganite (a polymorph of quartz).

Deposits of black onyx are found in many places around the world: Argentina, Australia, Brazil, Canada, China, Czech Republic, Germany, India, Indonesia, Italy, Madagascar, Mexico, Pakistan, Peru, South Africa, Thailand, Yemen, Uruguay, UK, and various states of USA.


Black onyx is opaque, highly glossy, but does not reflect light the way black diamond does. While it is vitreous, black onyx is also waxy when compared with black spinel.

Onyx is a variety of chalcedony that exhibits alternating parallel bands of colour, primarily black or white. Most black onyx is banded with white in its natural state, and is often dyed to emphasise or eliminate the banding. The alternating parallel bands of colour are harder to see in the black variety but do exist.


While silicate-layered chalcedonies are abundant, natural black onyx is actually exceedingly rare and is therefore the most sought-after variety by far. Due to this reason, natural black onyxes are seldom sold in the market today. Instead, dull or grey chalcedonies are treated to achieve the desired hue and sold as black onyx.

Popular cuts:

The opaque properties of black onyx make it a more suitable option for bead features. A lot of the time, black onyx is used for more of a centrestone in a larger piece. Other popular cuts for the black onyx include round, square, oval, trillion and marquise.

Maintenance and care:

A large proportion of the onyx available on the market nowadays is dyed to enhance its black hue and should therefore be cared for the same way as all colour-enhanced stones, by cleaning with warm water and mild soap, then rinsed thoroughly and dried with a soft cloth. Do not use chemicals, ultrasonic or steam cleaners.

Black onyx is rated 6.5-7 on the Mohs Hardness Scale, meaning that it has slightly above-average hardness and durability though slightly less so than black spinel which will be introduced in the next section. Owing to its moderate hardness, black onyx jewellery should be stored separately.

Black Spinel

While spinels are most commonly known to be red, being the third birthstone of August, the stone actually comes in a wide range of colours, with black spinel being one of the rarest minerals from the spinel family and one of the rarest naturally occurring true gemstones on the planet. The black spinel is a lesser-known gemstone due to its rarity and is commonly mistaken for black diamonds due to its opaque, jet-black appearance.

Much like its mysterious appearance, the origin to its name is also a mystery. It is said that the name ‘spinel’ comes from the Latin word ‘spina’ translating to thorn, or ‘spinella’ meaning little thorn, referring to the sharp crystal formations it is made up of. Others speculate that the name comes from the Greek word σπίν(ν)ος (spínos), which means to sparkle or spark.

Although black spinel is a rare commodity, it is not as valuable as sapphire and ruby. Nonetheless, in recent years, there has been an increase in demand and its value continues to increase with time due to its low supply.

Black spinel is often regarded as a protective gemstone that can repel negativity and trigger empowerment and inspiration to its bearer. There is also a popular belief that this stone can heal the entire body as a whole.

Raw Black Spinel

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As a naturally occurring mineral, black spinel is formed by metamorphic activity happening when molten rock combines with limestone or dolomites. During this process, a durable mineral is deposited within the rock itself. This mineral is mined for the rare black gemstone known as black spinel, which is made of magnesium aluminium oxide or magnesium aluminate. While black spinel is mostly found as water-worn pebbles, it can also occur as octahedral crystal formations.

Spinel can be found on several continents, from Kenya, Nigeria and Madagascar in Africa, to Brazil in South America, and especially across south Asia, from Afghanistan and Nepal, to Thailand, Cambodia and Burma. It has been commonly found in gravel beds in Sri Lanka, Tanzania, and Madagascar, and marble deposits in Vietnam. Smaller deposits are found in the USA, Australia, etc.


Black spinel is described as having similar qualities to sapphires and rubies and is usually mined alongside these two precious stones. In fact, it was only in 1783 when the spinel was recognised as a separate mineral from ruby, as identified by the famous mineralogist Jean Baptiste Louis Rome de Lisle.

High-quality black spinels rarely have inclusions, but when they occur, it results in a beautiful star effect called ‘asterism’. The fact that the black spinel has few inclusions means it is very durable and resistant to scratching. Spinel crystals are highly reflective, giving off a vitreous (glass-like) lustre and sparkle.


Aside from the deep black hue, spinel can also be found in a broad range of colours, from saturated reds, pinks, violets, lavenders, light to dark blue tones, greens, browns, to amber and yellow hues.

The black spinel has a distinctive black colouration, ranging from an inky black to a stark dark that resembles the night sky. This rare gemstone has a pure black hue with no secondary tones, and it doesn’t require any enhancement so that it can have its jet black colour. Due to black spinel’s highly reflective property, it does not display any metallic overtone – a unique feature rarely seen with other black gemstones.

Popular cuts:

Due to its lack of cleavage and uniform nature, black spinel is perfect for faceting, through which the gemstone can be transformed to display a stunning reflection of light.

The black spinel can offer many shapes including the common ones such as round, oval, pear, and cushion cuts. It is also available in fancier cuts like baguette, trillion, octagon, kite, and marquise.

Maintenance and care:

Black spinel has a rating of 8 on the Mohs Hardness Scale, meaning it is a relatively hard and durable mineral and is less susceptible to surface scratching.

Black spinels can simply be cleaned using a soft cloth along with warm soapy water, then rinsed thoroughly to remove the soapy residue. Relatively speaking, black spinel is rather stable when exposed to various chemicals and light, but there may be some issues with high heat. Therefore, steam or ultrasonic cleaners can be used, but are not recommended because heat and vibrations can damage the gemstone.

In terms of storing black spinels, each stone or each piece of black spinel jewellery should be stored separately with a soft cloth or pouch because despite the stone’s relatively good durability, black spinels of the same hardness can still scratch each other.

Feel free to get in touch with Laine Jewellery for recommendations and advice on diamonds or customised rings! I offer free consultation services every Friday at my studio at Two IFC, bookings required. Interested parties please make a reservation through Whatsapp or Laine Jewellery’s Facebook page!

Whatsapp: +852 6819 2038


Elaine 💌


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