Back to IGS | FAQ | Contact

Practical Exam Assistance


#1

Does anyone have advice on the practical exam given by IGS. I have the RI’s of the gems and am not looking to purchase any further equipment besides what I already have such as Loupe, Karat scales, Refractometer. My interest is in Rough chunks of gemstones and tumbled stones which I am asked to identify for people all the time. These gems are more jewellery and jewellers faceted gems. Any advise is greatly appreciated.


#2

Learning to identifying rough is more challenging than identifying faceted gems. Learning to identify faceted gems first would help. As for the tools and the Practical Exam, we recommend as a minimum the equipment in Recommended Gemology Tools and Instruments. Good luck.


#3

Is the software an essential purchase for the course?


#4

The software Gemology Tools is not essential, but it is useful.


#5

Without more clues than what your current equipment offers there may be some difficulty. There are many overlapping measurements between different stones on any one piece of equipment. While the software may be a guide to gemstone identification it certainly is not a final authority. It can in fact be misleading if you focus on the database information only. It is a good tool just like many others. Measuring SG, magnetism, thermal conductance are most helpful along with lots of visual characteristics that can only be observed under magnification with a microscope, loop, dark field loop… and so on. Some clues you can only see with magnification like the shape of an inclusion. So with all that said, see the list of recommended gemology tools and instruments, and plan a few more. I wish you luck with your endeavors.


#6

Many Thanks for your reply. It seems a plethora of equipment is needed to finish the course. I appreciate your input and info on the database information.


#7

I think you can pretty easily ID rough with what you have…if you’ve cu a window in the rough and determined the RI, then you can also determine birefringence and dispersion with the refractometer, and also optic sign and optic character. This, along with a visual examination with magnification, should tell you what you need to know. It is also possible, using a small plastic cup of water, a little thread and the tare function on your scale, to determine an SG. Weigh the specimen suspended in the water, then weigh it sitting on the bottom of the cup, and compute SG. You can spend almost nothing to get a tile for determining streak and use a few common objects around the home (copper penny, knife, piece of quartz, various synthetic gems) to develop a set of hardness points which you can use to estimate hardness. Light from a cell phone is polarized, so get a white screen app and, placing your specimen on the phone, use the lens from a pair of polarized sunglasses to give you a polariscope and you can determine SR vs DR or ADR that way. I disagree that it is tougher to ID rough than cut stones and you can see why I say that above.
If you are willing to spend a liittle more money, get a purple/UV laser to determine long wave UV response and buy a standard magnet for determining magnetic susceptibilty (go to gemstonemagnetism,com). You could also consider getting a strainless sphere (acrylic ball) and cutting a side off a plastic box (or use cellophane from the florist) for a quartz wedge simulator to determine optic sign and character with your cell phone polariscope. I think you can find instructions for that on line. The more gemology you know, the fewer tools you need. All of this stuff (except the magnetic stuff) is in Hanneman’s book, Affordable Gemology, but probably the hints I’ve given here will do for the resourceful. SG plus optic sign and character with appearance, hardness and inclusions should tell you all you need to know. The UV laser and magnet are added, easy tests. Forty bucks on ebay will get you a dichroscope and spectroscope, should you want to play some more. Help, I’m talking about gemology and can’t shut up…LOL
royjohn


#8

Hi,
Thank You for your help and great response. I too don’t agree with the response about rough being harder to identify than the faceted ones in the exam as I do it all the time. If someone brings a piece of Kyanite (for example) I look and say it’s a piece of Kyante or that’s a piece of Azurite and Malachite mixed. The practical exam in no way helps rough identification. I really appreciate your input.