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Quartz-So Common and yet so Special

Flawless Quartz Crystal Sphere at the Smithsonian Natural History Museum (106.75 lbs)

Flawless Quartz Crystal Sphere at the Smithsonian Natural History Museum (106.75 lbs)

This crystal sphere is the largest cut piece of  flawless quartz in the world, weighing in at 242,323 carats!  It symbolizes our fascination with something so beautiful and yet so common.  Quartz is found around the world, in large quantities, and is considered one of the most common minerals on Earth.  It’s found in sand, dirt, and dust.  Yet, when fashioned by gem cutters and put in a stunning piece of jewelry, it can be breathtaking.

Quartz is a complicated gemstone.  One of the reasons it’s tricky is because the term “quartz” is used for varieties of gems, as well as for a species of gem and as a group of gems.  So, for example, Rose Quartz is a variety of the species Quartz.  So is Citrine, Amethyst, and Tiger’s Eye!  All these varieties, and others that are couched under the species of Chalcedony, such as Agate and Jasper, are considered to be members of the group, Quartz.  Very confusing!!

Perhaps it’s best to start with the fact that mineralogists and geologists see any mineral with the chemical makeup of silicon dioxide, SiO2, as Quartz.  Regardless of whether the crystals making up that stone are large, small, or microscopic, it’s all Quartz.  Gemologists, on the other hand, separate the gems into those whose crystals are larger and those too small to see without a high-powered microscope.  Those with larger crystals are called Quartz and those with microcrystalline structures are labeled Chalcedony.

Under these two species are many varieties that are used in jewelry.  Probably the most commonly known variety of the quartz species is Amethyst.  That regal purple has been admired for centuries.  The purple color comes from natural irradiation acting upon a trace element of iron.  The saturated, medium to deep reddish purple is the most prized color, but amethyst ranges from a light, pinkish purple to that deep purple hue.  Amethyst is not rare, but the prized color is more rare because usually only the tips of the amethyst crystals have that depth of color.

Agate and Amethyst, showing the deep purple tips of the quartz crystals, as well as the microcrystalline Agate, which is part of the Chalcedony species.

Agate and Amethyst, showing the deep purple tips of the quartz crystals, as well as the microcrystalline Agate, which is part of the Chalcedony species.

Other varieties of the Quartz species include Citrine, the orange-yellow gemstone that’s November’s birthstone, and Rock Crystal, which is colorless because it has no trace elements.  There’s also Rose Quartz, Smoky Quartz, Prasiolite (aka Green Amethyst), and Ametrine (a bi-colored gem combining the purple of Amethyst and the yellow of Citrine).

Members the Chalcedony species have been used in jewelry even longer than Amethyst!  Agates, which exhibit wavy bands of color, were used in amulets and talismans over 3000 years ago.  They were also used to make cameos.  Carvers would reveal a differently colored band by carving down around the subject of the piece.  Today you’ll see agate slice pendants that are sometimes dyed to accentuate the banding.

Probably the most valuable member of the Chalcedony species is Chrysoprase.  This translucent gemstone is beloved for its natural apple-green color.  It owes its color to the presence of  nickel.  A big discovery of Chrysoprase was made in 1965 in Australia.  Because its color can resemble fine jadeite, it’s sometimes called “Australian Jade.”

Chrysoprase cabochon

Chrysoprase cabochon

Other varieties of the Chalcedony species include Black Onyx (dyed black chalcedony), Carnelian, Jasper, and Fire Agate.  Most chalcedony is translucent to opaque, so it’s rarely faceted.  Most often it’s fashioned into beads, slices or cabochons.  But, just like all Quartz, it registers a 7 on the Mohs Hardness Scale, making it a good choice for rings and bracelets as well as earrings and pendants.

There’s so much that can be said about this beautiful mineral that surrounds us everyday.  But I want to end with the sentiment– “How wonderful when something so common can also be so special!”

Custom-made Ametrine Ring in our showcase!

Custom-made Ametrine Ring in our showcase!

 

The Gift of Quartz

sand

Is it hard to believe that something as common as sand or dust is made of, basically, the same ingredients as the most beautiful amethyst?  Silica and oxygen are two of the most common elements on Earth, and they are the two needed to form quartz, a group of minerals which contains, among other gemstones, amethyst.  What a gift that, sometimes, the simplest and most common ingredients make an awe-inspiring product.

The “Quartz Family” is a wide-ranging group.  Amethyst is part of the large or single crystal strand of this group, along with citrine, smoky quartz, rock quartz (colorless quartz), and prasiolite (green quartz).  These are the quartz gemstones that are likely to be faceted in order to refract light.  They are more transparent, being cut from a single crystal.  There are two main reasons why these gemstones are different hues.  Trace elements such as iron can mingle with the silica and oxygen to influence the color.  Heat and/or irradiation acting on the mineral can also change its color.  Citrine, for example, is generally made by heat-treating pale amethyst.

Another branch of the quartz group is the microcrystalline strand.  Gemstones like tiger’s eye and aventurine are aggregates of many, many small quartz crystals.  These gemstones are generally translucent or opaque and are rarely faceted.  You might see them carved into cabochons or made into beads.  Colorless quartzite is an aggregate that is often dyed in various colors, sometimes to mimic other gemstones like jade.

Gemstones with cryptocrystalline structure have crystals too small to be seen without a powerful microscope.  Chalcedony, agate, and chrysoprase fall into this strand.  Chalcedony comes in various colors, both naturally and with man’s help.  Chrome chalcedony is naturally green due to a trace element of chromium.  But black onyx is actually chalcedony that has been dyed black.  Chrysoprase, one of the most valuable gemstones in the quartz group, is a translucent apple-green due to the presence of nickel.  These gemstones are sometimes faceted but usually are made into cabochons, beads or other carvings.  Agate, a multi-colored banded gemstone, can be used to carve cameos.

Quartz comes from almost every corner of the globe.  South America, North America, Australia, Africa, Asia, and even Europe all have deposits of quartz.  Because it’s so plentiful, even in large pieces, quartz is generally affordable.  We often think that the more expensive something is, the more beautiful it must be.  But that’s just not true in the case of quartz!

amethyst