Gemstone Identification

[R_G_Bargy]

I'll try and explain best I can. I use a small cardboard box about 150mm(6") square with one side removed, leaving 5 side intact. Using 2 cheap polarizing lenses, I cut a hole to fit them firmly in opposite sides of the box. Keeping them in line so when a light is shone though one it will also go through the other. With the light (a torch or the like) placed facing up, put the box on top with a lens in the center. Now look from above rotate the top lens and you will see it go from light to dark as the 2 polarizes go into opposite directions. With them placed so they are not letting any light through, you take a stone hold it with your finger tips and hold it mid way between the lenses. Rotate the stone around horizontally. If it's double refractive it will go light and dark as it's rotated, nothing happens to a single refractive stone. With a zircon it has one direction of single refraction. One needs to find this if the stone is to be cut, cause if a stone is cut in a direction of double refraction the facets are doubled and the stone will look fuzzy. If I can find where I put mine I'll put up a photo. Hopefully this is as clear as mud

 

[R_G_Bargy]

Shown with one lens in and one out.

Note how dark the top lens is with the 2 polarizes correctly oriented.
Hopefully this helps

 

[Nugget]

Great information and pics RGB, thanks.

 

[R_G_Bargy]

You're most welcome!

 

[Jed]

Many thanks RGB your instructions & pics were clear to me - very much appreciated - cheers Jed

 

[Heatho]

Great info, thanks.

 

[R_G_Bargy]

If anyone makes one, let us know how you go.

 

[richo966]

I was told to look for black spinal in the pan did that picked one up and it was blue so happy for that bit of info thank you who that was cant remember but good tip found nothing until I read that bit helped a lot cant wait to go back to gg for another trip would like to know more so I can teach people and help others find there first gem made me happy like to do that for some one one day

 

[Philski]

A simple field test is to look at its crystal structure with a loupe if you have one and if they are not too waterworn.
Zircon are tetra. (4 sided to a point) Garnet is cubic, like a box. Ruby, sapphire etc (Corundum) is Trigonal like quartz
The green ones look like Peridot or gem olivine and form in Basalt.

Another test is specific gravity or where it sits in the pan. Zircon is heavier than corundum, then garnet, quartz. etc
another test is a streak test. And, hardness test. Some are too close to call so some gemological tool may be needed. You can buy complete gemological kits from ebay for around $120
Or quality ones from GIA and GAA for several hundred, but will last a lifetime.

The refractive index can be measured with a refractometer. Whether its double or single refraction, a polariscope,
a dichroscopes is always handy too. Chelsey filters and ruby filters etc

Gemstone Identification is a matter of cutting down the variables, what shape, what colour, is it heavy, what colour streak, is it double refractive, how hard, etc.

I use my gemologist kit for cut gemstones predominantly to see if its a genuine stone or been treated at some stage than as a field kit. But still handy to have at home to be sure.

There is also an Australian book with a very good gemstone identification key. But i cant find it at the moment and cant remember the exact title. Getting old will look for you today. Its an excellent resource\

have a great day
Phillip

 

[Gold689]

Hi Philski, Great info there thank you for sharing

A quick note on alluvial gemstones in area like GG Creek, are most of them is tumbled or crack in half and some dog tooth for sapphires.

Over the course of time tumbling around the creek they lose their natural shape. Even without their natural sided shape they still look beautiful 8)
And many thanks to members here who's kind enough to share the photo's of their gems

Give's us an idea what they look like,..

Cheers,
"B"

 

[Mansfield123]

Any ideas on what this is. ?

 

[Wally69]

Rose Quartz ???

 

[SneakyCuttlefish]

Looks like some pink beryl I have been handling recently.

 

[AtomRat]

Looks like some pink beryl I have been handling recently.

There is some beryl in my books mentioning mansfield, could be. Looks a little too waxy to be quartz but does look like a rose as well!
We always recommend to check out and use the specific gravity test for unknowns:

https://www.prospectingaustralia.com/forum/viewtopic.php?id=17698

 

[Heatho]

Rose Quartz.

 

[Mansfield123]

Actually found it in the bendigo area

 

[Prospectinglife]

sorry about the quality ive had to minimize it from my phone to be able to post it. Im unsure to wether these are garnets or zircons as to the blue im pretty sure that could be a sapphire

 

[Prospectinglife]

this isnt the best image but all i can get at the moment as my girlfriend has them at her house. im not sure they go from pink purple blue brown and white all are clear bar the quarts.

 

[Prospectinglife]

there are some rose quarts in this bag, still not the best quality but best i can do at the moment.

 

[westatrest]

that one smack bang in the middle looks like a sapph to me, the others look like zircons and quartz..
what area did you find them?