Jewelry, Gems, & Minerals/Authenticate Emerald Heirloom Ring
Hello, I am hoping that you can help me authenticate (visually) a ring that my father's mother gave to my mother. I am hoping to use the stone for a my engagement ring, but am not totally convinced it is authentic. On the inside of the ring it say 18KT and HGE so it's "gold plated." I am also a science teacher and we are beginning Geology, I would love to use this as a lesson of how to identify stones in class if you have any suggestions for how I can test it (streak, Mohs Hardness Scale...etc.) I have more pictures if needed.
Thank you so much for you help!
I will try to provide a few basic tests and considerations in gemstone identification.
1.The first clue as to authenticity of the stone is based on the company it keeps.
Size Chart: http://www.gemselect.com/calibrated-size/calibrated-size-chart.php
Using the size chart, it is fair to say if an emerald, your stone is over 7 carats. Remember, the carat weight is based on an average weight for a stone of a particular dimension. Not fully considered is the depth or proportions of the gem. A deep stone will be more carats and a shallow stone may be of considerably less carat weight. Now visit the site of the gem seller and see prices and appearance of actual emeralds for sale.
Note how clarity and color affect the prices.
This site is for a gem seller. Look at the emeralds shown and see about how much per carat the stone is priced. Do you see gems with a similar look to yours? How are those priced? Go to eBay and search for loose emeralds gemstones. Search anyplace you can think of to see loose cut emeralds for sale. It will be very, very difficult to find a gem as large as yours and with similar color and clarity. If you find one, the price will be very high.
Being completely fair, would you even imagine a gemstone worth several thousands of dollars to be set in a gold plated mounting? (I do congratulate you on knowing that HGE is heavy gold electroplate. Even a few jewelers confuse the 18k as metal quality when it in fact only references the electroplate layer.)
Would the person who had the stone previously be likely to own a very expensive emerald?
2. Physical testing. This includes several testing methods which are out of the practical range of this answer, however, a few tests and observations are possible. The first is one you mentioned: MOHS hardness.
School and Teacher supply stores have lower cost Mohs kits. This test is relatively easy but you must use care that any scratch is at a normally hidden part of the gem. You do not want to damage the stone.
A porcelain dish with a slightly rough back side will work for a streak test.
Clean the stone well with detergent and rinse it off. Using a magnifier lens look as well as possible at the girdle(waist ) and at the facets on the bottom area where two facets come together and at the bottom in general. We are looking for telltale signs for glass. Are the meets or lines between facets rounded as in molded pressed glass or sharp as should be for a cut gemstone? Do you see any marks or lines on the girdle suggesting the stone was pressed into its form from hot glass?
Does the school have a means of testing specific gravity? This is a good test but the stone must be out of the mounting.
Is there a microscope for looking at the stone? If so, use transmitted light and look for round bubbles as seen in molded glass. Look on the Internet for “inclusions in emeralds” to use as a visual guide. There is a pretty definite need for at least some of the typical “jardin” or garden look in emeralds. You can see how on the seller’s site how clarity is affected by extensive inclusions.
A Chelsea filter will help. This dark glass filter will show red or pink for an emerald. The color agent in emerald is Chromium and causes red to show when other colors are filtered out of view. The problem is these handy little testing devices are not generally less than $20.
My first impression is size and clarity say the stone is not an emerald. Then again, I do not have the stone in hand to examine more closely.
What I have given is not a complete testing procedure. With the correct (and costly) equipment, the refractive index may be verified to close in on the id. Evenso, the basic examinations mentioned combined with the Mohs hardness should be sufficient.
Thanks for the question. Best wishes with the testing.
God Bless and Peace. Thomas.