A 10 x jeweler's loupe (pronounced as LOOP) is a type of magnification glass. 

It is small enough to carry in a pocket or purse.  I highly recommend using it when you buy gemstones and jewelry.  I think it is the wisest (and cheapest) investment for your gem purchase.  These loupes are available on eBay.  With it, you can clearly see a lot of things about gemstones and jewelry that you can never see with the naked eye.

I regularly use it for:

• Examining rough stones to determine clarity and orientation.

• Evaluating the quality of gemstones such as clarity, make of the stones, i.e., cut and polish.

• Detecting scratch, chipping and abrasion on gemstones.

• Checking the meet points and polish, when I facet a gemstone.

• Examining the condition of jewelry such as loose prongs, broken metal parts etc.

• Finding the hallmark of platinum, silver and gold.

It is also useful for other applications that require a close, magnified look.  It is really a handy gadget.  But you need to know how to use it.  It is a little tricky for the first time.  People tend to hold the loupe like the magnification glass used by the famous fictional detective, Sherlock Holmes. It won't work that way, because its focus distance is very short and you cannot get a good focus.  That is why I am writing this guide.

The type of loupe you should get.

It should be a 10 x (or ten power) triplet loupe.  "Triplet" means the loupe actually consists of three lenses.  That gives you a view without distortion.  I recommend black one, because it does not reflect the color on the stone. 

In my experience one that comes with a small leather case is usually better quality than one coming with a plastic case.  The price of one with a leather case is slightly more expensive, but worth paying. 

This is my Jeweler's loupe.  It has been working well for me for countless years.

• Loupes of higher magnifications are available.  But you don't need them, because the US Federal Trade Commission requires the grading to be done under 10 x magnification.  If you don't see any scratch on a stone under 10 x magnification, the stone is considered as scratch-free, even though there are some scratches detectable under magnifications larger than 10. 
• Also the higher the magnification is, the shorter the focus distance is.  That makes those higher magnification loupes VERY difficult to get a good focus on parts you want to see.  You might think that you can see the object better with a higher magnification glass.  That is yes only with a lot of practice using it. 
• I have heard a story that a deceptive jeweler let a customer use his 30 x loupe on purpose.  It looked like the jeweler was honest to disclose any defect on a gemstone he was selling .  The customer untrained with that type of loupe couldn't see the stone clearly and believed whatever the jeweler said.  

How to see an object with a 10 x jeweler's loupe.

• Hold the loupe with the thumb and forefinger of either of the hands.

• I am right-handed and use my right hand.

• Hold the object (a gemstone or piece of jewelry) in the same manner with the other hand.  You may need to use a gem forceps to examine a gemstone.  This way you can hold a small stone more securely, and avoid your finger oil getting on the stone as well. 

• I use my left hand.

• Bring the loupe as close to your eye as you can. 

• You should try each of your eyes.  You will find a more comfortable side.  I use my left eye.  So the knuckle of my right forefinger touches my forehead between my eyes, and my palm is facing outward.  That is my comfortable and stable hand position.  Some people have the palm inward lightly resting the heel of the palm by the mouth.   You will find your own good position.  You can keep your eyeglasses on while doing this.

• Look into the lens as if you are looking through a peep hole.

• At this point, the view through the loupe should be blurry.

• Keeping the loupe in this position, bring the object about 1 inch from your loupe.

• Get the focus by moving the object SLOWLY closer or farther.

• You should get a clear view of the object by now.  Practice focusing on the surface of the stone (polish) and in the stone (inclusions).  How about the cutting edges (chipping and abrasion)?  How do the facet lines come together (tightness of meet points)?

• Try different lightings to experiment how the object looks like.

• Of course, do not look at the sun or light source through the loupe.  It is not good for your eyes.

• On my last regular eye check-up, I asked my ophthalmologist if constant use of a loupe has any bad effect on the eye.  He said no.

Good luck with your loupe.  There is a totally different world through the loupe.

This guide is updated from time to time, when more information becomes available.  If you learned something new and useful from this guide, please click "yes" below.  Thank you!!