Black Tourmaline? Obsidian? How to Tell the Difference

Translucent (see the shadow?) Black Obsidian (L), Black Tourmaline Nugget (R)

Black Tourmaline and Black Obsidian are two of several gemstones that are shiny and black, and they can appear somewhat similar. So how can you tell the difference? I recently had an encounter with a customer who felt that the black tourmaline necklace she purchased was obsidian and not tourmaline (although it was definitely tourmaline!).  Well, in case other people are also confused regarding the difference between Black Tourmaline (a mineral) and Black Obsidian ("mineraloid" natural volcanic glass), here is some information I hope you find helpful!

BLACK TOURMALINE
Tourmaline is a beautiful gemstone that comes in many colors, and since it can't be created in a lab (so only natural Tourmaline is found), it can be very expensive.  Black Tourmaline, or "Schorl", is an inexpensive type of genuine Tourmaline---it's a rich black opaque color, and is found in abundance all over the world.  Sometimes in bright light you can see glints of red--that's due to iron in the gem. It grows within host rock, in large crystals, small crystals, and in various nugget and chunk forms.  Rough tourmaline can be left to look rough, or it can be polished, sliced, or faceted.  If you are looking for Tourmaline to wear for its metaphysical properties, Black Tourmaline is a great and affordable choice.

Here are some examples of Black Tourmaline----if you google that, you can see a very wide variety of  sizes and shapes of tourmaline nuggets, crystals, shards, etc.  Here are pictures of rough chunks of Black tourmaline, taken from various geologic and gemstone websites:

That last picture is from an Etsy seller---a very reputable, large-volume gemstone seller, who correctly describes these as "Tourmaline Gemstone Top-Drilled Large Raw Shards. Semi-Precious Gemstones."

And here is the actual strand of these types of "shards" of rough black Tourmaline that I purchased from another lovely seller on Etsy:

And it was one of those shards in that strand (right in the front!) that I sold to the one Amazon buyer who claims it's "obsidian".  As you can see, these shards look the SAME as the rough pictured above---especially in pictures 3 and 4!  These shards have been sliced and polished on the back, and the rough "lumpy" part is on the front.

Here is my favorite picture of tourmaline "in the rough".  It's a picture taken from the GIA website (Gemological Institute of America) in an article discussing Emeralds...but here is a large growth of Black Tormaline, plus Emerald, Mica, Pyrite and Quartz.  But look at the "lumpy" as well as "crystal" nature of this large Tourmaline find:

I love how this shows the wide variety of shapes and forms of Black Tourmaline.  It also shows the distinctive "lumpy" rough texture that the tourmaline shards that I purchased exhibit.  The upper right looks almost like burnt bark---and sort of like black lava rock! I would LOVE to have a piece of that beautiful emerald!!!

There are "crystals" of black Tourmaline as well.  These are found and sold in large nuggets, with more of a hexagonal crystal structure visible, and sometimes with crystal "tubes" than run along the length of the nugget. Often they look a lot like pieces of black licorice.  Some are very shiny and black.  Often they have very visible fractures and other surface cracks and flaws.  Here are some examples:

So you can see a wide variety of Black Tourmaline shapes---from crystals to nuggets to lumps and shards.


OBSIDIAN
Black Obsidian is black volcanic glass.  It is translucent--not completely opaque.  It's considered to be a mineraloid gemstone despite the fact that there is no mineral crystal structure in glass.  But it is natural, very shiny and black (and can also be smokey grey, brown, rusty red, banded, with "snowflakes" and in other colors).  Obsidian has a smooth uniform texture, and breaks with "conchoidal fractures" or semi-circular patterns.  This is distinctive to obsidian and glass:

Now, both black tourmaline and obsidian are black and shiny.  But obsidian does NOT have the rough and lumpy texture that tourmaline has.  Plus, when obsidian is carved or split or broken, it fractures in distinctive round radiating circles---like when  you toss a rock into a lake.

Incidentally, the value for black tourmaline and black obsidian is about the same, although there are many instances where obsidian is far more valuable than black tourmaline.  Obsidian is often used in making black opal doublets and triplets.

Obsidian, being glass, is VERY sharp when broken, so there is no such thing as "shards" of obsidian that are drilled and sold as pendants.  (Haha---reminds me of the old SNL skit about a terrible kids' toy called "Bag O' Glass"!)   There are polished obsidian beads.  Most obsidian is sold in chunks for gem collectors.

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So really, it's pretty easy to tell Black Tourmaline from Black Obsidian, just from the pictures!  And having it examined by a gemologist would tell you FOR SURE if it's glass or a mineral.  

Other gems that look very similar to these black gems are Black Onyx and Hematite, and even Black Spinel.  Chalcedony quartz is sometimes dyed black to look like Black Onyx.

Tourmaline is a beautiful gemstone and comes in many colors, including multi-hued gems such as Watermelon Tourmaline.   Here are some incredibly beautiful shards of genuine tourmaline, and the price for these on Etsy (they are about dime-sized) is just under $1,000:

Don't they look like stained glass shards?  They're so beautiful!  And definitely NOT glass!!