Malachite

Malachite is a green opaque gem. It crystallize in the monocline system.

The name comes from the Greek MALAKE’, that means mallow, of which it has the color of the leafs. Its main characteristic is the curved bands pattern in several green tones, from light to dark one. the color is given by the main component, copper, in the past it’s used to be found in deposits near to this metal. Thanks to its colour is considered the gem symbol of hope, love and faith.

 

The hardness is 3 and a half on the Mohs scale and, because sometimes it is found in big blocks, is quite often carved to get cameos, art crafts and statuettes.

The toughness is quite low, that’s why it must be handled with care. It can be ruined by chemicals, especially acids. It is also quite sensitive to heat and hot water.

In the past the main source of Malachite used to be Russia, but now new deposits are in Africa, Australia and USA. The best samples come from Shaba, Kenia.

Sometimes is found along with the stone Azurite; the match create a stone called Azurmalachite.

In nature it is found in microcrystalline clusters consisting of fine needles. The exact scientific term that describes its natural form is Botroydal, which refers to its irregular nodules growth in concentric layers, which, once cut, show the banding pattern that characterizes it.

Historically, it has always been a popular gemstone since the ancient Greeks and Romans, who used it for carvings and ornaments that we can still see today. In Latin culture it used to be associated with the Goddess Venus, they believed it can help to reunify lovers and also console those who have lost their loved one.

Was also used as an amulet to protect the owner from danger and especially to protect children, since the time of Solinus it was suggested to put it directly in the cradle of infants; also, to be placed near the woman womb to support conception and childbirth. According to ancient beliefs it  could be pulverized and dissolved in milk to help with heart disease, or mixed with honey and applied to wounds to promote healing.

When  in the 18th century rich deposits were found in Russia, the mineral became the favorite ornamental stone by the court of the Tsar. An example of this are the great pillars of the church of St. Isaac in Leningrad.

Malachite is considered a semi-precious gemstone and maybe this is the reason why nobody never created a synthetic version, but in the market there are many other cheaper alternatives, such as plastic, glass or dyed agate.

The only type of treatment that is applied to enhance the appearance is the impregnation with mineral oils to make the surface shiny and smooth.

Ruby

RaffaelloSanzio: Portrait of Maddalena Doni

The name Ruby comes from the Latin Ruber, which means “red”. Medieval Europeans wore ruby to succeed in Love, health and wealth.  Because of its color has always been associated with passion, love and beauty. It is the world most famous and best-loved red gem. 

 

Is the most important colored stone in the market and is the red variety of the gem species Corundum. 

The quality of a ruby is determined by different factors, the most important is the color.  The finest Ruby has a vivid red color with a light purple hint. In its purest form, the corundum is colorless, but if some trace elements stick into the crystal’s structure, the mineral can have some change in color. In the case of Ruby, the trace element that affects the red color is the Chromium. The saturation of the color depends of the quantity of Chromium present in the Corundum.  Because the Chromium causes fluorescence, the best ruby must have also some traces of Iron, which inhibits the fluorescence. 

Its hardness is 9 on the Mohs scale, is the hardest stone on Earth after the Diamond.

Historically the best quality color ruby comes from the Burmese source, which is described as “pigeon’s blood”.  Even though the origin of a Ruby is important to guarantee the quality, not only Myanmar produces high quality gems, any ruby source can produce both high and low quality stones.

The major sources of Ruby are in Asia: Myanmar, Thailand, Sri Lanka, Cambodia, and Pakistan.

 

There are mines also in Africa: Madagascar, Kenya, Malawi and Tanzania.

 

Natural Rubies are very often included, and is also difficult find it in big specimen. It’s rare see an eye clean ruby in exceptional size.  The environment where the ruby forms makes it difficult, for the crystal, to grow.

But the story is different for the sapphire, the brother of Ruby; the blue stone is easily found in bigger size and less included.

 

Treatments are widely used to enhance the beauty of the Ruby, and the heat treatment is now so common that is accepted in the trade, actually in every gem market it is assumed that all rubies are heated, unless there is a certificated that can prove it. Heat has multiple benefits; it works in both color and clarity. Any brown shades, that lower the quality, disappear to bring out the red color; while also the inclusions become less visible. Other used treatments, less accepted from the trade, are dyeing and fracture filling. 

Can happen sometimes, to see in the market the star ruby, the phenomena, called asterism,  is caused by the needle-like inclusions into the stone, if is cut into a cabochon the light is reflected in a 6-rays star. Those gems are highly priced and very rare.

Ruby and star ruby are both the US birthstones of July.

Ruby is one of the earliest colored stones to be imitated, with both natural and synthetic materials.  Glass is the most common material used as imitator. Other material are: red spinel, garnet, CZ, and dyed corundum.

Red Spinel

 

Garnet

 

CZ - Cubic Zirconia

In late 19teen century, some scientist introduced in the market a new kind of rubies manmade in lab. They found the way to synthesize in the lab what Mother Nature makes in million years. The process is quick and cheap.  Those synthetic rubies are now easily affordable, not expensive and look really good to the untrained eye. But don’t worries, the gemologist has the knowledge to distinguish between those and a natural one, if you want to buy a jewel with Ruby, always ask for a certificated, just to be sure!

Turquoise

Turquoise is one of the most ancient gems. Archaeologist found royal jewellery made in turquoise older than 7000 years ago. Chinese artisan carves it since 3000 year ago and is the national gem of Tibet. Is considered a stone that guarantees health, fortune and protection from evil.

In southwest US, native American tribes was used as medium of exchange, and also for jewellery and amulets. The apaches believed that turquoise enhanced a warrior’s accuracy.

The gem’s name comes from the French expression pierre turques, Turkish stone, because the gem first arrived in Europe from Turkish source.

The stone can be translucent to opaque, and has a unique light blue color. The blue is not always uniform, it’s actually often mottled and with dark splotches. It might also have veins of matrix.  The quality is judged on color, texture and absence of matrix.

The blue color is caused by the presents of copper, while the iron makes the stone look more greenish and lower the quality.

The color can be unstable, it can darken, fade or became green, depending on the other foreign substance that are absorbed from the stone.

The color changing is caused by the porous surface, that can also affect the durability. On the Mohs scale its hardness is 5 to 6, perfect to be worn but with care.

Matrix veins are often visible, even though cutters always try to fashion the final gems without it.

Turquoise gem is not so rare, but is very difficult find really high quality (that are highly priced on the market). Treatments are very common either to enhance beauty and to make them resistant to foreign agents.

Wax impregnation is the most used treatment. The wax improve luster, seal the pores and avoid contact with skin,  perfume and water; if you have any jewel in turquoise please pay attention  when you wear it: contact with sweat or cosmetics may damage them irreversibly.

Gem with light color are dye impregnated , but this technique is actually not used often, because the result looks unnatural and it doesn’t last.

The first historical source of Turquoise is Persia, but now the most important mines are in southwest US and China, where comes the specimen of highest quality.

Like any other gem , even turquoise has its synthetics and imitations. we said that the market is full of turquoise, but not of high quality samples; which is why in the ’80 was created the Gilson synthetic Turquoise. The material is produced by a ceramic method and has an artificial appearance, actually it was never widely available on the market.  Instead, the imitation are very common in the market, both natural and synthetic. The natural gems that most resemble the turquoise are: Variscite, dyed howlite and chrysocolla. Among the most widely synthetic used are glass and plastic.

dyed Howlite

Variscite

Chrysocolla

Lapis Lazuli

Man first discovered lapis lazuli almost 7,000 years ago. It has been found in ancient civilizations such as Egypt, Persia, Greece, Rome and the Middle East. 

It’s an easy, workable stone, so it’s not used only in jewelry, but also carving, mosaics, ornaments. It is also processed to make blue pigments for make-up and painting.

In Egyptian culture, this stone has an important connection with religion. Archaeologists found abundant amulets and talismans made in Lapis.

Its vivid blue color made it an important component of some European masterpieces. The frescos of some important medieval churches in Italy were made using the blue pigment made from lapis lazuli.  It is pretty impressive if you consider that at that time the Lapis was really expensive and was available only from one far source: Afghanistan.

Lapis lazuli is not a gem, but a rock, which means that it is an aggregate of several minerals, including but not limited to: Lazurite, Calcite and Pyrite. The quality of the stone is determined by the percentage of these three minerals. For example, if the calcite matrix is too present in the stone, it looks white and therefore less appealing.

Lazurite

pyrite

calcite

The presence of the pyrite flakes makes the stone look like a sky full stars, and this is the reason why people believed that the stone unleashed peace and  relieved stress. Kings and queens used it in the past as a powerful status symbol; it was considered a piece of heaven given to men by the gods.

The top quality color is a violetish blue with no-visible calcite and some gold looking pyrite flecks. The presence of an excess of calcite or pyrite can lower the quality of the stone and make it look greenish and less valuable. Its hardness is 5 to 6 on the Mohs scale.

It can be found in different shades of blue, depending on the other minerals in the aggregate.

On Earth, there are not many Lapis mines: the finest quality is found in Afghanistan, the oldest source, but it is found also in Chile and Russia.

Because fine-quality Lapis stones are highly priced, treatments are common, but not stable, which makes the treated stone less valuable than untreated one. The dyeing treatment is used frequently; it’s used to enhance the blue coloration and cover the white coloration caused by the calcite but can be rubbed away with acetone. Usually after dyeing, it is also impregnated with wax to protect the stone and make it appear shiny.

Gilson 

Lapis imitations are plenty and are old as lapis itself. Glass, plastic and ceramic are very common in the market, they are manmade at a low cost.  Another manmade material created just to imitate Lapis is the Gilson Imitation Lapis Lazuli, which apparently looks just like the original, but is actually very porous. Is Its hardness is 3 on the Mohs scale and the luster is dull. The color is perfectly even and the pyrite flakes appear like sprinkles on the surface. Other substitutes are Chalcedony and sodalite.

Until the 1950s it was one of the December birthstones, so it can be used as a good alternative to Tanzanite and Turquoise for people who were born in that month.

Tourmaline

Probably, tourmaline has been used in jewellery for centuries because people confused it with other gems. 

For example, in the 15^th century was discovered in Brazil a deposit of green tourmaline that Portuguese thought was Emerald.

Fortunately in late 18^th century tourmaline found its identity, thanks’ to the work of a gemologist who wrote about this special gem.

The name comes from “toromalli”, the Sinhalese word for “mixed gems”.

It comes in different colors, actually is the gem with the widest color range of all. It has several shades of almost every hue. And very often it has colors that you can’t find in other natural gemstones.

 Some colors have their own trade names:

rubellite

paraiba

Rubellite: with colors that go from pink to red and purple.

Paraiba tourmaline: take the name from its source, the color is a bright violetish blue o greenish blue.

Watermelon tourmaline: has a pink centre and a green outline.

 Indicolite: is dark violetish blue.

indicolite

watermellon tourmaline

parti-colored tourmaline

Parti-colored tourmaline: has more than one color, it has a vary combination, the most common are green and pink. The color zoning happen when trace elements change composition during the crystal’s growth.

pleochoic colors visible under
dicroscope lents

The crystal has usually an elongated shape, which force cutters to create an elongated final shape and proportion. The rectangular is the typical cut.

But when the crystal is well formed, is not cut, for collectors it has more value than fashioned gems.

Tourmaline is pleochroic: which means that depends from the point of view, it  looks in a different color, usually one of the pleochroic colors is slightly darker than the other.

The cutters have to pay attention to the pleochroism, they have to finish the gem giving the best color from the top right view.

Brazil is probably the largest producer of tourmaline of the world. One of its products is the Rubellite, the trade name for pink-red tourmaline.

In 1989, a rare blue tourmaline has been discovered in Paraiba state, the color is so rare and attractive that very quick this stone became the most priced gem of the market.

When the chemical composition of tourmaline has some chromium as trace elements that cause the color of the gem, in the trade is called chrome tourmaline. The hue of the crystal goes from bluish-green to yellowish green. Like the Paraiba one, this variety is relatively new in the market, it started to appear in late 1960’s.

If the stone has some needle like inclusions and is cut properly, it can shows the phenomena of the cat’s eye: the inclusions reflects the light as a bright line that resemble the eye of a cat.

The two most used treatments of tourmaline are heat and irradiation. They are never used to change the hue of the stone, but actually to lighten and brighten the original color. For example, many Paraiba tourmalines are treated to remove some greyish hint and give a spectacular bright blue color.

Usually those treatments are stable and undetectable.

Tourmaline is a piezoelectric material, that’s why you can see lighters, flat iron or watch made with those crystals.

Topaz

Topaz

The Topaz has always been part of many cultures with different significance all over the world.

Topaz crystal

The ancient Greeks believed that it gives them strength. During renaissance people used it to break magic spells and in India, for centuries, people worn topaz above the heart to have a long life.

In US is the November birthstone, with the Citrine, and it is a talisman for the sign of Sagittarius.

Some research believe the origin of the name comes from the Sanskrit “Tupaz” which means fire.

Some other says it comes from the island S. John, once called Topazios, in the red sea, were was abundant of an olivine stone, confused with Topaz.

Imperial Topaz

sherry Topaz

Always, the topaz has been associated with the yellow color, so all yellow stones were topaz. But Now we know the topaz comes in a wide color range which includes different shades of red, pink, orange, yellow, purple, green and blue. Can also be colorless.

When the stone is found in peachy orange color, in the trade is called Imperial topaz.

But if is found in yellow to orange color is called Precious Topaz.

In the shades of brownish yellow is called sherry topaz, from the color of the sherry wine.

Topaz crystals have an elongated shape, that’s why usually the stone is cut as long ovals, pears or emerald cut. Most colors are available in some standard shapes, but there is a difference in size from color to color.

Is commonly colorless, but treatment can produce the blue color. Naturally blue gems are extremely rare. From ‘70s those treatments gave to the market a big quantities of uniform blue gems that matches the manufacturers demand.

The most used treatment is heat, alone or in combination with some irradiations.

Usually, yellow stones are heated to make pink colors, and colorless topaz are heated and irradiated to create blue shades.

Of course the final colors depend from the original shade and saturation.

In the Mohs scale topaz’s hardness is 8, which is perfect for an everyday jewellery. Topaz is an hard stone but be careful anyway, its toughness is poor, it can be broke due to its cleavage.

Usually does not have specific inclusions, big stones can easily be eye clean and bright clear.

The most important source of fine quality topaz is in Brazil, in the Ouro Preto area. Since the middle age to the XIX century, topaz price was really high, till the brazil’s source was discovered.

Other sources are Pakistan and Sri Lanka.

The Crystal can be very big, we can find 2 famous examples displayed in New York (300kg) and in Florence (150 kg).

Is very often confused with Citrine and smoky quartz, its inexpensive substitutes, the color yellow is similar but in topaz has a warm undertone. Because very often exchanged with its substitute some people get surprised when see a topaz jewel with an expensive price, Citrine is so abundant that is very easy get a big nice stone with a low budget, topaz is more rare.

Treated Topaz

Is important to know that topaz can change its color due to irradiation and heat, but don’t be worried to wear it during summer, the heat must be over 400° C to see some changes. But if anyway you prefer to have back the original color, you have just to expose the stone to the UV irradiation.

Is improbable find in the market a synthetic topaz, some lab made few samples only for scientific purposes; is actually more common see substitute such as natural quartz and Spinel, or even synthetic Spinel, glass and synthetic sapphire.