Pearls – the Birthstone of June

How can June nearly be over?! It was still snow outside like literally two months ago! We sort of skipped spring here in Sweden and went straight to scorching summer temperatures which was quite a chock for this gal here who isn’t built for such warm weather.

Anyway. June. A month which not only has one but TWO birthstones: moonstone and pearl, and today it will all be about the forever timeless pearl.

Freshwater pearl jewellery set in 14k gold fill.

“Pearls are always appropriate” – Jackie Kennedy

 Pearls are with no doubt the most timeless, classic and sophisticated gem out there. It is regarded as one of the true precious gemstones together with diamonds, rubies, sapphires and emeralds and might even be the best-loved gem of all time.

Top: simple baroque freshwater pearl pendant paired with a luxurious 14k gold fill chain with elongated links. Bottom: handknotted freshwater and baroque pearl necklace using white silk thread and finished with a modern and minimal sterling silver toggle clasp.

 

Pearls – the beautiful result of a defence mechanism

First things first, what is a pearl?

A pearl is in fact an organic gem that forms inside of a living saltwater or freshwater mollusk.

Pearls are made up of concentric layers of calcium carbonate, CaCO₃, either aragonite or a mixture of aragonite and calcite. The layers are held together by an organic horn-like compound called conchiolin. The combination of the two (calcium carbonate + conchiolin) is called nachre –  the stuff that makes up the beautifully iridescent mother-of-pearl.

Left: the calcium carbonate mineral aragonite, here in crystal form. Top right: natural pearls in cross section clearly showing their concentric rings all the way through to the center of the pearl. Bottom right: the beautiful iridescence of nachre – Mother of Pearl.

 

The formation of a pearl begins with an irritant inside of the mollusk. The irritant could be organic, a parasite or a tiny speck of sand that found its way inside.

As soon as an irritant settle on the soft tissue it gets enveloped by a pearl sac – a layer of mantle tissue cells which make up the protective membrane on the inside of the mollusk shells. The pearl sac acts as a defence mechanism which seals the irritant off from doing any harm and then nachre is secreted, layer by layer, slowly building up a pearl. Typically, the build-up of a naturally forming pearl takes a couple of years.

Pearl sacs that eventually will become full grown pearls.

 

Perfect shining little spheres of delight

Due to the unique conditions under which natural pearls form they come in a dazzling array of sizes, colours and shapes. Perfectly round ones are actually very rare.

Below I’ve listed some of the most basic shapes:

• Round
• Semi-round
• Button
• Drop
• Pear
• Oval
• Baroque
• Circled

Perfectly round pearls are the rarest and most valuable shape. Semi-rounds are often used in necklaces or in pieces where the shape of the pearl can be disguised to look lite it’s a perfectly round pearl. Button pearls are like a slightly flattened round pearl. Drop and pear-shaped pearls are sometimes referred to as teardrop pearls. Baroque pearls are often highly irregular with unique and interesting shapes. Circled pearls are characterized by concentric ridges, or rings, around the body of the pearl.

The many shapes of pearls. Bottom right from the left: circled, baroque, button, drop and round.

 

Natural vs. cultured pearls

Natural pearls are nearly 100% calcium carbonate and conchiolin (nachre) grown in concentric layers by mollusks in the wild with no human involvement. Natural pearls are actually incredibly rare, and in the past many hundreds of pearl oysters or mussels had to be gathered and opened, and thus killed, to find even one wild pearl. Their scarcity was the reason for their then extraordinarily high prices.

Today natural pearling is confined mostly to seas off Bahrain and Australia, and to spare any mollusks not carrying pearls all mollusks goes through an X-ray examination in order to reveal any hidden pearls within.

Left: antique natural pearl and 19ct gold necklace. Right: antique natural pearl necklace with diamond clasp.

 

Cultured pearls are formed in pearl farms, using human intervention as well as natural processes.

In the pearl farms, a tiny piece of mantle tissue from a donor mollusk is implanted into the recipient mollusk to kickstart the pearl-forming process. To get perfectly round pearls, they often use spherical beads of mother-of-pearl as the nucleus. The use of an implant like this enables cultured pearls to be harvested much faster, just after six months.

Top: pearl farming in Fiji. Bottom: pearl extraction process.

 

Cultured pearls can be distinguished from natural pearls by X-ray examination since their interior gives them away.

Since cultured pearls are often ‘preformed’ they tend to follow the shape of the implant. When a cultured pearl with a bead nucleus is X-rayed, it reveals a different structure to that of a natural pearl. A beaded cultured pearl shows a solid centre with no concentric growth rings, whereas a natural pearl shows concentric growth rings all throughout. Their interior is of course also visible if you cut the pearl in half.

Top: illustration of the difference in interior between a cultured and natural pearl. Bottom left: cultured pearl cut in half clearly lacking concentric rings. Bottom right: natural pearls in cross section with obvious concentric rings all the way to the center.

 

Pearls, pearls, pearls!

The vast majority of pearls sold today are cultured in pearl farms and comprises mainly of four types: akoya, South Sea, Tahitian and freshwater.

Akoya

Pinctada fucata (akoya pearl oyster)

• Introduced to the market in 1916 as the first ever spherical cultured pearl
• Bead and non-bead cultured
• Environment: pristine saltwater far from cities
• Location: Japan and China, larger sized pearls (≥ 8.5 mm) are generally from Japan
• Colours: white or cream, some with hints of pink or green
• Size: generally between 3-7mm but can occasionally reach 9-10mm

Top: a classic white pearl necklace made with akoya pearls. Bottom left: akoya pearl in her akoya oyster shell. Bottom right: the subtle overtones of the akoya pearls: silver, rose and cream.

 

South Sea

Pinctada maxima (silver- or gold-lipped pearl oyster)

• Culturing began: 1950s
• Bead and non-bead cultured
• Environment: saltwater
• Location: between the northern coast of Australia to the southern coast of Southeast Asia passing the Phillipines as well as Myanmar
• Colours: silver, white and golden
• Size: generally between 8-16mm but can very occasionally reach over 20mm

Left: golden South Sea pearls on top of the golden-lipped oyster shell. Right: the golden colour scheme of the South Sea pearl.

 

Tahitian pearls

Pinctada margaritifera (black-lipped pearl oyster)

• Culturing began: 1960s
• Bead and non-bead cultured
• Environment: tropical saltwater, preferably clean-water lagoons
• Location: French Polynesia
• Colours: eggplant purple, peacock green, metallic grey and greyish blue
• Size: generally between 7-12mm but can very occasionally reach over 16mm

Top left: baroque Tahitian pearls. Top right: beautiful Tahitian drop pearl pendants made by Malin Ivarsson. Bottom right: the many overtones of Tahitian pearls. Bottom left: a Tahitian pearl in the shell of a black-lipped oyster.

 

Freshwater pearls

Hyriopsis cumingii or hybrid

• Appeared on the market in 1971
• Bead and non-bead cultured
• Environment: freshwater, usually cultured in lakes and ponds
• Location: China, Japan and Tennessee, U.S.A.
• Occur in a wide range of sizes, shapes and colours

Top and bottom left: the many shapes and colours of freshwater pearls. Bottom right: each freshwater pearl oyster can grow several pearls at once, resulting in a high production and thus cheaper prize.

 

How to care for your pearls

Pearls are, due to their soft calcium carbonate mineralogy, unfortunately easily scratched. Therefore they need to be handled extra carefully, both when wearing and when storing them, in order to maintain their beauty.

A first rule of thumb when dressing is: pearls should be the last thing you put on and the first thing you take off. This rule can and should be applied to all kinds of gemstone jewellery to maintain their beauty.

Below is a few pointers to keep in mind for keeping your pearls looking shiny and new to last a lifetime.

Cleaning

• For routine care, after each wearing, wipe your pearls with a very soft and clean cloth to remove any residues from the skin.
• For occasional, thorough cleaning, use warm and soapy water . If the pearls are strung, be sure the silk is completely dry before wearing.

Storing

• Store pearls separately from gems and metal jewellery, which may scratch their surface. Instead, store them wrapped in a piece of silk or satin.
• Never store pearls in a plastic bag. Plastic can emit a chemical that will damage their surface. The same is true of cotton wool.
• Never store pearls in a well-sealed box for a long time. Like your skin, pearls need a little moisture so they will not dry out.

Wearing

• Pearls can be damaged by many chemicals and all acids. The list includes hair spray, perfume, cosmetics and even sweat. Always apply perfume, hair products and perfume before putting on your pearl jewellery. And remember, this can be applied to all gemstone jewellery.

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There, this post turned out quite long and I don’t blame you if you just skimmed it. But if you read the whole thing, THANK YOU!

The blog post about June’s second birthstone, the moonstone, need to unfortunately be postponed. I’m busy busy preparing for a rock and jewellery show that’s taking place in a month’s time, I hope you don’t mind. To see some behind the scenes on me hustling away you are more than welcome to stalk me on instagram 🙂

Until next time, I wish you a wonderful summer!

♥ Linda

April Birthstone – Diamond

Finally! I’ve had so much going on in my life the past two months (moving, preparing for a presentation, started working again) that I have not had the time to finish and publish the April birthstone blog post. But better late than never they say so here you go!

And now this one is gonna be a goodie, I love the science behind diamonds – science that is super unique, cool and that still has scientists wondering! But I had to cut back on the info that I had originally written because I tend to be an over achiever and not know when to stop, don’t worry though, you’ll still get plenty much of fun and interesting facts about this famous gemstone!

Diamond jewellery made with raw silvery grey 2-3mm Diamonds and 14k gold fill. Delicate birthstone jewellery for everyday wear. Handmade by me.

But first I need to be honest with you. I’ve never been that interested in diamonds, diamond jewellery that is. Particularly diamond jewellery with diamonds that fulfil all of the four C’s perfectly. But give me a diamond with a “flaw”, a rough surface, with some interesting inclusions or a more unique cut and shape, and I’ll be completely captivated and drooling over the floor!

Now, let’s start with some back story of the diamond gemstone.

The History of Diamonds

Diamonds have likely been known for as long as 6000 years and are thought to have been first discovered in India. There diamonds were found in alluvial deposits* along rivers. In the early days the diamonds were used as religious icons as well as in engraving tools due to their great hardness.

Ancient diamond jewellery. Left: Roman diamond ring from the 3rd-4th Century AD. Right: Indian diamond pendant necklace (www.pinsdaddy.com).

The popularity of the diamond started to rise significantly from the middle of the 19^th century when diamonds where found in South Africa. Due to increased supply, improved cutting and polishing techniques, growth in the world economy, and innovative and successful advertising campaigns it quickly became the most valued and popular gemstone.

                   “Diamonds are a girl’s best friend.”

                                                       “Diamonds are forever.”

Today diamonds are mainly used for two things: personal adornment and industrial use.

*Alluvial deposits are vast deposits consisting of eroded material that’s been transported by gravity and water and accumulated in the base of a mountain.

Diamond Science

A diamond is a crystallised form of carbon (C) within the cubic crystal system. It’s the hardest natural material known to man, mostly due to the strong covalent bonding between the atoms in its diamond cubic crystal structure. This type of crystal structure is made up of a repeating pattern of 8 carbon atoms that the diamond adopts as it crystallises. This pattern is really hard to explain so I will not even try to go there and just leave you with this illustration of it below instead.

Visualization of the diamond cubic crystal system. By Cmglee, https://commons.wikimedia.org/w/index.php?curid=28157521

If grown unhibited their crystal structure enables them to grow into perfectly shaped crystals. The most common pure shapes are: cubes, octahedrals and dodecahedrons.

Three common diamond crystal shapes found: a cube (bottom left), an octahedron (upper right) and a dodecahedron (bottom right).

What I find really awesome though is that diamond as well as graphite are both solely made up of carbon, but diamond came to be the hardest material known to man while graphite is the softest, hence its use in pencils. This big difference in hardness has all to do with in which conditions (pressure and temperature) they were individually formed, which in turn decide their crystal structure and thus their hardness.

Fun fact: at the Surface of the Earth, graphite is actually the stable form whereas a diamond is actually metastable. This means that a diamond with time could convert to graphite. But don’t worry, this conversion would probably take billions of years which means your precious diamond jewellery is safe. Unless you have eternal life. And if you do, I want to know your secret!

Fun fact II: if a diamond gets engulfed by a fire it will literally burn up and only leave a pile of ash in its place.

Diamond Sources

Diamonds are extremely rare, with concentrations of at most parts per billion in their kimberlite host rock. Before the 20^th century most diamonds were found in alluvial deposits where they are found in much greater quantity. Loose diamonds are also found along existing and ancient shorelines, where they tend to accumulate because of their size and density.

Left: a diamond in its host rock, a kimberlite. Right: a diamond in a piece of sedimentary alluvial deposit.

Where and How Diamonds Form

Most diamonds come from the Earth’s mantle, where they form deep below the surface of the Earth (about 150 – 250 km) under immense pressures and temperatures. Diamond formation is favoured by a thick lithosphere (crust + the uppermost rigid layer of the mantle) which can be found in continental areas with old (2.5 billion years old or more) stabilised crust. Such geological features are called cratons and can be found within all of Earth’s continents.

Left: the layers of the Earth. Diamonds form within the lithosphere which is the topmost two layers. Right: Cross section of the lithosphere over a craton, showing its thickness and where the diamond formation zone is.

However, there are other sources. Some blocks of the crust, or terranes, have been buried so deep as the crust thickened that they experienced ultra-high-pressure metamorphism. These terranes have evenly distributed microdiamonds that show no sign of transport by magma.

Also, when meteorites strike the ground, the shock wave can produce high enough temperatures and pressures for microdiamonds and nanodiamonds to form. These types of diamonds can be used as an indicator of ancient impact craters.

Both these last two sources produce diamonds that are way too small to be used in the jewellery industry.

Surface Distribution

Diamonds are far from evenly distributed over the Earth. Though they are almost always found in kimberlites on the oldest part of cratons which makes them easier to find. Kimberlite is a type of volcanic rock that forms at even greater depths than diamonds. As the kimberlitic magma ascends during an eruption, any diamonds within its path gets caught.

World map showing the location of all kimberlites currently found.

The science behind kimberlite formation and how it ascends to the surface during an eruption is still not clear. But what scientists do know is that the whole eruption process has to be fast enough in order for diamonds to still be diamonds when they arrive at the surface of the Earth. If the eruption were to be too slow, the diamonds would have time to convert into graphite before arriving to the surface.

The Four C’s

As you may know, a diamond is graded based on the four C’s: carat, cut, colour and clarity. This method got developed in the 20^th century by expert gemmologists and is based on the characteristics most important to a diamonds value.

• Carat – a diamond’s weight, 1 ct = 200 mg
• Cut – the quality of the cut is graded according to proportions, symmetry and polish
• Colour – how close to white or colourless a diamond is; for coloured diamonds, how intense the hue is
• Clarity – how free a diamond is from inclusions

Apart from the four C’s, diamonds are also cut into different shapes which all reflects the light differently, giving each shape their own unique appearance and characteristics.

Diamond shapes.

Fun fact: a large (≥100 carats or 20 g) and flawless diamond is known as a paragon and such a diamond is considered to be a perfect diamond.

Fancy Colour Diamonds

Fancy colour diamonds are a collective name given to diamonds that display a colour. The rarest and most valuable colours are saturated pinks, blues and greens. In all cases, even very slight colour differences can have a big impact on value. Other colours that falls into the ‘Fancy Colour Diamond’ category is yellow, brown, red and blue. Red and blue diamonds are extremely rare whereas brown diamonds are the most common and yellow diamonds are the second most common.

Fancy coloured Diamonds in a variety of cuts and shapes (www.kimberfire.com).

Salt and Pepper

As I’ve already mentioned, a diamond that fulfil the four C’s doesn’t interest me that much. They are still beautiful but for me they lack that something extra: personality. I remember when I first started seeing included diamond jewellery on Instagram (where I hang out way too much these days) and I was amazed by their uniqueness, natural beauty and character. This particular diamond, named ‘Salt and Pepper’ diamond, first appeared on the market about 10 years ago and has been inching its way up in popularity ever since.

Dreamy Salt and Pepper Double Diamond Ring and Diamond Leaf Earrings by Katie Carder.

‘Salt and Pepper’ diamonds are characterized by white (salt) and black (pepper) inclusions scattered within and tend to be more silvery grey in colour rather than colourless. This type of diamond is often accompanied with a simpler type of cut such as a rose cut (my personal favourite cut btw).

Amazing rose cut diamonds in various shapes sold by Caleb B. Quashen.

A ‘Salt and Pepper’ diamond is not only beautiful, unusual or unique, it also shows you how beautiful flaws really can be and how they only add to their appearance.

So take it from these diamonds, flaws are BEAUTIFUL, they are a part of who you are, so let them be seen and be YOU!

Beautiful Salt and Pepper Diamond Rings by Meri from Gardens of the Sun.

Now, I’d love to hear what your favourite diamond looks like. Is it colourless or coloured, clear or included, raw or faceted? Please do leave a comment below and let me know!

With ♥

Linda

The February Birthstone – Amethyst

Welcome to blog post number two about birthstones (again, published in the last second). As you know I like to get science-y with these posts and probably use terms and jargons that you’ve never heard of. But I will try and explain everything as simple as possible for you. After all, I want you to understand what I’m talking about, so you can see why gemstones are so much more than just pretty minerals adorning the jewellery we wear.

 

 

How to not get drunk

February means it is all about the amethyst! Amethyst is, as many of you may know, the purple variety within the large quartz family with a simple chemical composition, namely SiO₂. Since it’s a quartz variety, it has a hardness of 7 which means it’s very suitable for jewellery since it doesn’t scratch easily from everyday wear.

Amethyst got its name from the ancient Greeks who thought amethyst would keep them from getting drunk. The word amethystos literally means “not intoxicate”. They would wear or drink out of amethyst vessels in the belief that it would prevent intoxication.

 

Left: carved amethyst wine goblet. Right: my amethyst earrings in sterling silver.

 

Ultra Violet

If you didn’t know, the Pantone colour of the year for 2018 is Ultra Violet, which suits the deep purple colour of the amethyst pretty well if I do say so myself. Amethysts come however in many different purple hues, from a light pinkish violet all the way to that royal deep purple. The most valued colour of amethyst is the deep purple one and a deep purple that has a red tinge to it.

So how does amethyst get its purple colour? Simply put it all has to do with the presence of iron in its structure. Iron atoms may replace silicon atoms during the crystal’s formation. And we are talking trace amounts here, the amethyst wouldn’t be an amethyst anymore if a major part of the silicon atoms were to be replaced.

One thing that you should be aware of when it comes to the colour of the amethyst is that if it gets overexposed to sunlight, it can fade in colour. So, if you want to keep that deep purple colour of your amethyst jewellery or mineral specimen pristine, display or store it in a place with little to no sunlight.

The ametrine

 

A rough ametrine specimen with a clearly visible border between the amethyst and the citrine halfs.

 

Have you ever heard of the gemstone ametrine? The ametrine is a gemstone that is half amethyst and half citrine, which means it displays both purple and yellowish hues. This dual colouring is due to differing oxidation states of the iron within the crystal. And the differing oxidation states occur during the crystal’s formation (its crystallisation phase), as the temperature gradient across the crystal cools over time.

The formation of an amethyst

Amethyst crystals are always grown onto a base within a cavity of a host rock. This sort of rock with a sparkling surprise inside is called a geode.

 

Amethyst geode from Brazil. The crystals are grown onto a base consisting of agate.

 

Geodes are round to elongated rock structures which are hollow inside with minerals lining the walls. The base of the mineral lining is usually thin bands of translucent grey and white agate which the crystals then grow on top on. Geodes range in size from under one centimetre to several meters in length. From the outside most geodes look like common rocks, but when they are opened the sight can be breath taking. The outer wall of a geode is more resistant to weathering than the surrounding bedrock which allows it to survive intact when the surrounding bedrock weathers away.

Apart from amethyst crystals, other common geode minerals include quartz, agate and calcite. Some rare geodes can be filled with beautiful blue gem silica, pink rhodocrosite, spectacular opal or other rare materials.

 

Two beautiful geodes with spectacular mineral landscapes within. To the left: a basalt geode with mesolite and chalcedony. To the right: a basalt geode with blue chalcedony, calcite and mordenite bobbles. Both from India.

 

The formation of a geode

I bet you wonder how on Earth there can exist hollow cavities within solid bedrock, so I will tell you. Most geodes are found in volcanic rock deposits such as basalts. These are rocks that normally contain a lot of gases and it’s the gases that creates these cavities. When the lava cools and solidifies, any gases that hasn’t been able to escape gets trapped and thus create cavities within. Another way a cavity can form in volcanic rocks is by liquid lava flowing out of a partially solidified lava flow. These ‘lava tube’ cavities produce some of the largest and longest geodes.

 

Several amethyst geodes within an ancient basaltic lava flow.

 

Geodes can also be found in sedimentary rocks such as limestones, dolomites and calcareous shale. Within these rocks, shells, tree branches, roots and other organic materials often decay away to leave a void. These geodes are generally smaller than the geodes formed in volcanic rocks.

What all of these cavities has in common is that their mineral lining is due from mineral rich hydrothermal water or groundwater finding their way in and precipitating mineral material over a long period of time. And it’s the mineralogy of the surrounding rocks and the minerals within the water that decides which minerals will form within the geode.

So, if you want to find some amethyst crystals yourself, look for geodes within old basaltic lava flows!

. . . . .

So that’s that – I hope you enjoyed this blog post and that I managed to make you look at an amethyst in a completely new way!

Linda