Monday, September 2, 2013

What's the Difference Between Topaz and Quartz?

Topaz and Quartz are both common minerals, and both are used in jewelry.  They both come in a variety of colors, and both are beautiful.  But what's the difference between these two minerals?

First off, Topaz is harder than Quartz.  Topaz has a Mohs hardness rating of 8, and Quartz is a 7.  There are a variety of colors of quartz, known by their common gemstone names, as follows:

  • Rock Crystal - or clear crystal quartz; can have inclusions, such as rutile or tourmaline; the most common type of quartz
  • Smoky Quartz - dark brown to grey to black; frequently included with rutile needles
  • Amethyst - purple, deep to light, violet; the most valuable of all quartz gems.
  • Ametrine - contains both amethyst (purple) and citrine (golden yellow)
  • Citrine - light yellow to deep golden brown; most citrine is heated amethyst.  If heated, has a reddish tint.
  • Lemon Quartz - sparkling golden "margarita" color, natural.  One of the very few genuine "fruity" quartz stones.
  • Prasiolite - leek green; NOT natural, always heated amethyst or light yellow quartz
  • Rose Quartz - light pink to strong pink; cloudy
  • Aventurine - green; red-brown; golden-brown; sparkling inclusions. Green often sold as "jade"
  • Blue Quartz - turbid (cloudy) blue; never clear.  Caused by crocidolite fibers
  • Tigers Eye - brown with gold "ray of light" on surface
  • Hawk's Eye, Cat's Eye - White, gray, green, yellow, brown Cat's Eye; blue-grey to blue-green in Hawk's Eye; like Tiger's Eye, caused by reflection of light by parallel fibers, needles, or channels.
Chrysocolla
  • Chalcedony - translucent quartz in blue,white, grey; bloodstone (dark green with red spots)
  • Agate - many colors included banded, onyx
  • Carnelian - red to orange to brown translucent stone
  • Chrysoprase - rich green, very often used to misrepresent jade
  • Chrysocolla Chalcedony, marketed as "Gem Silica":  relatively rare, blue to blue-green, opaque to near transparent material; the most expensive type of chalcedony.
Topaz is found in a variety of transparent to translucent colors: clear (colorless), white, pale blue, light green, yellow, yellowish brown, pink, or red.  It is a very hard stone which makes it wonderful for all types of jewelry.  Blue topaz is always irradiated to achieve the beautiful Swiss, Sky, and London Blue colors that are coveted.


I read a handy tip to tell if a stone is Topaz or not:

  • Clean the stone and dry it.
  • Using a rod or something small, place a drop of water on the surface of the stone.
  • If it's Topaz, or a stone that is harder than an 8 on the Mohs scale, the drop will just sit there.
  • If it's Quartz, or anything softer than an 8, the drop of water will disperse over the stone.
  • The harder the stone, the more rounded the drop of water!

Smoky Quartz
Generally, a topaz gemstone is more valuable than quartz.  An example of this is Smoky Quartz---many times, a seller will call it Smoky Topaz, but it is not.  There is no such gemstone as "Smoky Topaz".  It's actually a dark brown variety of Quartz!

So-Called "Tanzanite Blue Quartz"
Another example is Blue Topaz v. Blue Quartz.  Blue Topaz is much more valuable, clear and beautiful.  It is one of the most popular colored gemstones in the marketplace.  It has a striking luster and a range of beautiful blues that rival the very expensive Aquamarine.  But Blue Topaz is not a naturally-occurring gemstone.  The process used to achieve the deep blues is controversial (I've written about this previously) because it involves radioactivity.  However, recent testing reveals that Blue Topaz gemstones are perfectly safe to handle.


Blue Quartz with Tourmaline
Blue Quartz is quartz that contains blue minerals such as tourmaline, is blue because of the "Rayleigh scattering effect" caused by tiny inclusions, or a coarse grained, massive, macrocrystalline form of blue quartz similar to aventurine quartz that is also colored by embedded blue minerals, like dumortierite.

Blue Quartz varies in color from grey to deep blue, like navy blue.  Natural blue quartz is always colored by inclusions of other minerals.  Here (above right) is a picture of a double terminated quartz from Brazil.  It is deeply colored blue by inclusions of fine needles of indigolite, a blue tourmaline. From the Jenipapo Mine, Itanga, Minas Gerais, Brazil.

Chalcedony is a natural blue quartz.  Chalcedony blue quartz is milky, cloudy, not crystal clear.  

But what is the crystal clear "Blue Quartz" that is found in strands of faceted briolettes, or all kinds of jewelry?  Sometimes sellers call it "London Blue Quartz" or "Sky Blue Quartz" which are actually names of TOPAZ gemstones, not quartz.  Another example of "creative marketing" on the part of sellers, or vendors who supply sellers.  Actually, these are not gemstones at all----these are glass, sometimes called "Fused quartz".  The rough can be purchased with names such as "Blue Sapphire", "Cornflower Blue", "Electric Blue Topaz", "Cobalt", and more.  These can be seen HERE.  These have a Mohs rating of about 5 to 6.5, the same as window glass.

Hydrothermal quartz is synthetic quartz that is grown in a lab.  According to syntheticgems.org it has a Mohs rating of 7.  I have contacted some manufacturers of hydrothermal quartz, and I haven't found anyone who makes this for jewelry---it is strictly for industrial applications (grown for quartz watches, electronics, etc.).  So I'm not sure if I quite believe that so-called "hydrothermal quartz" exists in the jewelry world because I haven't found any proof of that.  I do know that "hydroquartz" is absolutely GLASS though, just like "fused Quartz" as I mentioned already.

"Mystic" Blue Quartz
Sometimes, clear "rock" quartz is coated with a blue "mystic" film to give it a blue tint with rainbow colors.  This is also not really "blue quartz" and the mystic coating will scratch off.  This is found often on etsy, and to me it looks weird up close---like the color has rubbed off on the facets or something.  It almost always looks like this.  And this picture is for a strand of new mystic quartz briolettes----imagine what they look like after wearing awhile!


Personally, I wouldn't buy any sort of "blue quartz" that is crystal clear.  I assume that it is glass.  I have no reason to think otherwise.  In the picture of the "Tanzanite Quartz" above, you can see tiny bubbles---a sure sign of glass.  One of the largest (if not THE largest) supplier of this "hydro blue quartz" is Alibaba in China, and we all know that they sell a lot of fakes and glass gems.  If I want a beautiful blue gem, I will buy Topaz or my favorite, Aquamarine.  These are real for sure!  And they have a value! 

So, buyer beware! 

2 comments:

  1. Thanks for sharing this information. I guess one thing I know for sure, topaz and quartz are both great and valuable gemstones. And they could both be made into beautiful pieces of jewelleries.

    SylvaRocks.net

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  2. They sure are gorgeous! If it sparkles, I love it!! (And if it's blue, even better!!)

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