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.

Jade: Jadeite and Nephrite

This stone had for thousand years a great significance specially in Asia.

It always been source of inspirations not only as material for art craft, but also for spiritual and religious meaning. In Asia, but mostly China, Jade has a very long tradition either  for weapons, tools, jewellery, ornaments and sculptures. Archaeologist found jade’s art craft even older than 7000 years ago.

In the past, the people use to be confused about jade; the word "jade" has been used to refer a two different minerals: jadeite and nephrite. Those material have a chemical composition very different from each other, but both are soft enough to be carved and tough enough to resist to impacts.

Chemically are very different, they belong to 2 different mineral species. In the trade the value of jadeite is way higher than nephrite, and it’s 3 most important qualities are: color, transparency and texture. 

Anytime we talk about jade, we think about a green stone, but actually jadeite comes in other colors, yellow red orange white brown gray black and lavender, which is the second color most popular. Of course, the green color is the most requested in the marked, the most valuable is an uniform intense green and high saturated, called imperial green, which is very rare.

white jade

lavender jade

black jade

orange jade

imperial green jade

The green color is caused by the presence of chromium, the same element that causes the color in emeralds.

Usually, black jadeite is carved, but starting from the 2000 Guatemala’s black jadeite began to be used also as gem in jewellery.

Of course, in the marked is more requested a jadeite with the best uniform color, so uneven colored stones are carved in statues and tools, and also cheap jewellery.

The transparency of the jadeite vary from semitransparent (which is the best) to opaque.

jade bangle

It texture can be from fine to coarse, depending on its crystal’s size. The crystal structure contributes to its texture and to its exceptional toughness. This is way is very often polished as beads, bangles or ring, one piece only, it very difficult find other stones with this properties.

jade ring

dyed jadeite

Treatments are widely common in jadeite: in the most used the jade is dip in melted wax to improve its luster and fill veins and pits. Other treatments are bleaching or dyeing the jadeite to enhance its color.

The sources of jadeite are several in the earth: the best quality comes from Myanmar, Guatemala is nowadays the major source of black jadeite, we have also in Russia and California.

nephrite

Nephrite is commonly called jade, just like jadeite, but this one have a completely different composition and structure, and is also widely common so it has a lower price.

Its color is less interesting than jadeite, usually darker, less uniform with low saturation. It’s rare see nephrite in jewellery, is usually used for carving tools and everyday objects.

Even for nephrite the sources are different in the world; the major are China, Canada and New Zealand.

nephrite

Be careful, because is an high requested gem, it easily switched with substitutes, those might have similar colors to the originals, but rather than this there are not other qualities like the original jade.

Serpentine

The most common substitutes in jewellery are Chrysoprase (a chalcedony variety) and green garnet; for carving is very popular the serpentine, called in the trade “Korean jade”.

Amber

Amber belongs to the organic gem’s group, so gems that are created by living organism (in this case plants) in a biological process. Is a resin of an extinct pine, which probably produced it in a huge quantity. This resin settled and hardened with time, holding within it all that she had incorporated when still soft, was in various crevices of barks or rocks around.

To be called “Amber” this resin can’t be younger than a million years!

It has been used ornamentally up to 13.000 years, mostly in northern Europe, and historically has been used (it is still now) also as perfume, medicine and cosmetics.

Amber is soft and warm to the touch. Because is not a mineral it doesn’t have a crystalline structure, actually its an amorphic (no shape). It’s very easy to work, very often the artisans make complex carvings that sometimes are real master-piece. 

The varieties vary slightly among the various fields. The color is very similar to honey, the most common is yellow to orange, but the most valuable is transparent red. Usually amber is quite transparent, is very easy see through all the inclusions (if there are), but sometimes Amber happen to be a bit cloudy that are enhanced in beauty with treatments.

Amber's popularity is due to its special inclusions. The gem is not expensive, indeed it is one of the cheapest, unless if small prehistoric creatures, that are now extinct, are trapped inside it.

Because comes as a soft and sticky material, it could happen to some insects or small animal to remain trapped along with leaves or other plants. Today these “guests” are real relics that help scientists discover more about our past and about the environment where they were formed.

Because every piece is unique, amber that contains this special inclusions hold on the market a price far higher than those clear and without inclusions.

The world’s leading source of Amber is in Northern Europe, the Baltic Sea Region. The past geological eras have changed the geography of the land but has retained all production of the prehistoric conifers that produced this special resin. Every time that occurs in the sea an erosion  some amber is released; its low specific gravity allows it to float in salt water, so, once on the surface, waves washes it to beaches where is possible collect them. 

Of course, this is not the only one way to find Amber. In the World there are several open-pit mines where the gem is mined directly from the ground. The other main sources of Amber in the world are: Dominican Republic, right now the most important, Mexico and also Italy, in Sicily Island, where the gem is called Simetite.

Hardness and toughness are very low, so if used in everyday jewellery needs care but not special maintenance. It is sensitive to heat, burns at low temperatures giving off a peasant scent; actually is often used as fragrance for incense.

IMPORTANT: beware of who wants to sell gems and marketing them for true Amber, and to prove their authenticity passes the flame of the lighter under the stone to show you that does not burn! It happened to me to see it, done by peddlers, and many people believe it! If it were really amber it would burn out quickly, and would also be irreparably damaged!

Sun Spangles within Amber

Treatments to enhance its beauty are very common, the most common are oil filling that clarifies cloudy gems and heating to lightens dark amber. Heating creates also inclusion called sun spangles.

We can find some different kind of imitators, either natural and manmade. The most common natural is the Copal, which is a natural resin younger than amber, it has less then a million years.

in this Ambroid is possible see some bees and olive's
leafs. if they were real inclusions in true Aber, this big
gem would be priceless!

 As manmade imitator plastic is the most used, this material resembles amber in many aspects; the only two things that make them different are the types of inclusions and their specific gravity: the plastic has a SG higher than amber, so it sink in salt water.

An object that is commonly found in jewellery is the Ambroid: small pieces of Amber are heated and gathered together  with high pressure: this technique makes not only a bigger gem, but also a gem that gives positive results to all identification tests, but is very easy to identify with magnification; usually some gas bubbles get trapped between the stones, which are visible at the loupe!  

The Quartz

The Quartz is the most common mineral, because it's made by two chemical elements: silicon and oxygen, which are abundant on Earth.

Quartz has many of different varieties which differ from each other from the size of their crystals.

all this varieties can be divided in three categories based on the size of their crystals:

·        Large single crystals.

·        Microcrystalline aggregates of small crystals.

·        Cryptocrystalline aggregates of very small crystals (invisible to the eye).

Even though share the same chemical structures and composition, each one of those categories has gems that looks very different from each other.

Single crystal.

Amethyst

Amethyst: has always been one of the most-prized gems, either for its vibrant color and for its affordable price, way much cheaper than rubies and sapphires.

The hues vary from a violetish purple to a reddish purple, which is the finest quality.

Usually, the amethysts that we see on the market are free of visible inclusions and even colored, even though sometimes is possible see a color zoning. the rough crystal is often color zoned, with the color concentrated on the tips. Amethyst are heat treated very often to improve their color, and also removes some brown hint that makes the stone less marketable.

The main sources of Amethyst are Brazil and Africa; in particular, Zambia produces the best qualities gems.

Brazilian's gems are usually medium-quality and usually are suitable for heat treatment that turn its color in a citrine's Yellow.

Citrine Quartz

Citrine: is very rare in nature and often is confused with topaz! Its beautiful yellow-orange color is caused from a trace of Iron in its chemical composition. The most prized Citrine is free of inclusion and color zoning. the best color is a saturated yellow to reddish orange.

Most citrine that we can found on jewelers are heat treated Amethyst.  

Ametrine Quartz

Ametrine: this gem contains both amethyst and Citrine colors. Cutters usually prefer polish the stone with an half-half effect that shows both colors. Bolivia is only one source of natural Ametrine in the World.

Some Ametrine we see on the market are the result of heat treatment and Irradiation of color-zoned Amethyst.

Smoky Quartz

Smoky Quartz: it used to be worn as mourning gem in late Victorian period. This quartz displays an orange-red pleochroic flashes. Because of its color very often is confused with topaz, but it’s much cheaper!

sometimes is heat treated to lighten the color and get a yellow hint similar to citrine.

Rose Quartz

Rose Quartz: of this variety the color range goes from light to dark pink. When the crystal is found transparent and inclusion free, is usually faceted and used in jewels.

When contains small inclusions it can sometimes shows asterism with a six-pointed star.

the best quality usually comes from Brazil.

Rock Crystal

Rutilate Quartz

Rock Crystal: is the colorless transparent quartz, usually inclusion free. This variety is abundant and usually is found in big size. in the past has been used very often as a Diamond simulant.Sometimes has some eye-visible inclusions, that don’t affect to the gem’s value, actually contributes to increase its value. Is this case the gem is called Sagenitic Quartz and in the trade get different names according to the different type of inclusion you can fine inside. For example,  a very popular one is the Rutilate Quartz: rutile’s crystals looks like a needle-like inclusion and inside the quartz creates this fascinating designs. Rock crystal are often heated and Dyed to get a color similar to stones more expensive, this treatment is called Quench-Crack.

Microcrystalline aggregates.

Gems that belongs to this variety are made by more small crystals connected to each other that, with some needle-like inclusions, usually interact with light producing some fascinating optical effects.

Tiger’s eye: the surface of this semi-translucent stone has a pattern of yellow and brown bands that reverse the color if the stone is turned. Actually, of this stone, we can have different varieties, like grayish blue (hawk’s eye). The phenomena of Chatoyancy that characterizes those gems is caused by their fibrous structures oriented parallel.

Aventurine quartz: in this gem the aventurescence is caused by some small mica inclusions that reflects the light.

Cryptocrystalline aggregates

The chalcedony is a cryptocrystalline quartz, it means that is an aggregate of crystals so tiny that are invisible to naked-eye. The rough chalcedony has a very unusual structure, called botryoidal, that looks like a bunch of grapes. Because is made from the mix of a lot of tiny different crystals, the final gem can display different bodycolors and different pattern from translucent to opaque.

Carnelian

Chrysoprase

As translucent gems there are some in just one uniform color like the intense green of Chrysoprase, the vibrant blue of the Chrysocolla-in-Chalcedony and the warm brownish color of Carnelian and Sard.

Crysocolla-in-Chalcedony

Aggiungi didascalia

There are two varieties of Chalcedony that display parallel stripes of contrasting colors: Onyx, with black and white bands, and Sardonyx, with brown and white bands. This color banding make this gems suitable for cameos and other carving designs.

Agate in Geode

Agate is also a chalcedony with banded structures which can vary in color and transparency, and the bands are not parallel, actually they are curved and irregular. Collectors love this stone because of the magnificent pattern that it displays; sometimes the stripes create scenery that resemble real landscape! 

Agate is found in deposit call Geode. 

Fire Agate, it displays Iridescence

Dendritic Agate

Moss Agate

All this differences produces a big variety of Agates like: Moss Agate, Dendritic Agate and fire agate that displays iridescence.                                   

Leopard Jasper

The completely opaque chalcedony, doesn’t matter which color, is called Jasper. Sometimes the Jasper displays on its surface a pattern that resemble the coat of the leopard, this stone is called on the trade Leopard Jasper. 

Bloodstone

The Bloodstone is a special variety of Jasper. It has a dark green bodycolor and is characterized by some dark red spots that resemble drops of blood.