What are some identifying features of sapphire?

[violeta978]

I am new to Pricescope - this is in fact my first thread. I am not sure if there's a similar thread already.

I learnt a lot about choosing sapphires, but what are some of the identifying features of a sapphire that sets them apart from other gems?

 

[chrono]

Violeta,
I am unsure what you mean by your question. Do you mean in a gemmological fashion (inclusion, growth lines, specific gravity, refractive index, etc.) or something else? Or do mean how to tell a sapphire apart from a garnet, spinel, tourmaline, etc at a glance without using any tools?

 

[violeta978]

Chrono,
Yes, I meant in a gemmological fashion. Now that you mentioned “how to tell a sapphire apart from a garnet, spinel, tourmaline, etc at a glance without using any tools” I’d like to know that too - only if it isn't too much trouble. Gems are so fascinating.

 

[eastjavaman]

Without using any tools?????? At the very least you will need 10x Loupe. Or You can try to scratch the sapphire to glass(Not recommended, Do this at your own risk ) or scratch them against each other based on their hardness , Diamond will be the hardest based on Mohs scale; thus, it will scratch the other stones.
All gems come in variety of colors; thus, it is nearly impossible to discern them without using tools. In the older days Red Spinel was thought to be Ruby due to eye observation alone.

 

[chrono]

General information.
http://www.palagems.com/sapphire_connoisseurship.htm#sapphire_buying_guide

There are a ton of interesting subpages in the Ruby-Sapphire page.
http://www.ruby-sapphire.com

I don't like to ID any stones by sight alone but sometimes there are signs and clues when looking at a particular gem that hints at the possibility of it being a spinel or sapphire or garnet or tourmaline or something else when evaluating the dispersion, lustre, pleochroism, doubly or singly refractive, potential zoning and etc. Again, this is far from a proper evaluation and I see it more as something interesting or fun to do to get the mind thinking. Consider this a geeky behaviour by a gem lover.

 

[minousbijoux]

General information.
http://www.palagems.com/sapphire_connoisseurship.htm#sapphire_buying_guide

There are a ton of interesting subpages in the Ruby-Sapphire page.
http://www.ruby-sapphire.com

I don't like to ID any stones by sight alone but sometimes there are signs and clues when looking at a particular gem that hints at the possibility of it being a spinel or sapphire or garnet or tourmaline or something else when evaluating the dispersion, lustre, pleochroism, doubly or singly refractive, potential zoning and etc. Again, this is far from a proper evaluation and I see it more as something interesting or fun to do to get the mind thinking. Consider this a geeky behaviour by a gem lover.

I would go one step further and say without tools, this cannot be done with any certainty.

 

[LD]

I'd go a few steps further as well and say that in order to assess a gemstone at home (if you have a loupe and a few other basic tools) you may still have difficulty interpreting what you're seeing. For example some treated stones have gas bubbles BUT some natural spinels have bubbles too! Identification at home can be fun but for your results to be semi-accurate you need to have seen in person many different examples of both natural, treated and synthetic stones of each species. Some treatments will not show up with tools and need specialist lab equipment. Unfortunately knowledge doesn't come overnight and this is why the advice on this forum is always to send to a lab if in doubt.

Having said that I would urge anybody interested in gemstones to purchase a few tools so they can have fun trying to pre-determine the outcome a lab might confirm!

 

[violeta978]

Mmm.. I was initially asking for any facts that gemmologist use to identify a sapphire.

 

[kenny]

Mmm.. I was initially asking for any facts that gemmologist use to identify a sapphire.

Perhaps this is too obvious ........ hardness of 9 on the mohs scale.
A sapphire will scratch anything softer than 9 and can be scratched by anything harder than 9.

That said, I'm not recommending damaging valuable polished gems by scratch tests.

 

[chrono]

Specific gravity of 4.00
Refractive Index of 1.762 to 1.770
Crystal structure is hexagonal
Strongly dichrioc

 

[violeta978]

Thanks Crono and Kenny. No, I wouldn't want to scratch my tourmaline.
Crono dichrioc means?

 

[chrono]

Dichroic means you see one colour when viewed down one axis, and a different colour when viewed down a different axis. Look at the stone from the table to see one colour. Turn it sideways and you'll see a different colour. You'll need to use a dichroscope to help see this characteristic though.

 

[minousbijoux]

it sounds like you are interested in learning about the specific gemological properties of sapphires. There is a website which has Gemology in the title which you will find helpful, I'm sure. As part of the website, they have a learning/educational tool called "The Gemology Project." I have found it to be just about the best teaching tool around and have learned quite a bit there. I suggest you google that phrase and see what comes up. Oh, and their search tools are excellent.