Colored Gems Weight Estimation Tables To obtain approximate weights of the following shapes of colored stones multiply by the following measurements to millimeters. A listing of the specific gravities is below. Round Faceted = ...................Diameter x diameter x depth x SG x .0018 Oval Faceted = .......................Diameter x diameter x depth x SG x .0020 Emerald Faceted = .................Length x width x depth x SG x .0025 Rectangle Faceted = .............Length x width x depth x SG x .0026 Square Faceted = ...................Length x width x depth x SG x .0025 Marquise Faceted = ...............Length x width x depth x SG x .0017 Pear Faceted = ........................Length x width x depth x SG x .0018 Heart Faceted = ......................Length x width x depth x SG x .0018 Table of Specific Gravities for Popular Gemstones Zircon: ........4.32 - 4.70 Diamond: ................3.52 Conch Pearl: ............2.85 Almandite Garnet: 4.05 Peridot: ....................3.34 Turquoise: .................2.76 Ruby: ......................4.00 Jadeite: .....................3.34 Lapis Lazuli: .............2.75 Sapphire: ................4.00 Zoisite (tanzanite) ..3.35 Beryl Group: ............2.72 Malachite: ..............3.95 Diopside: .................3.29 Pearl: ..........................2.70 Rhodolite Garnet: 3.84 Spodumene: ............3.18 Quartz: .......................2.66 Pyrope Garnet: .....3.78 Andalusite: ...............3.17 Coral: .........................2.65 Chrysoberyl: .........3.73 Tourmaline: .............3.06 Iolite: ..........................2.61 Spinel: ....................3.60 Nephrite: ..................2.95 Opal: ..........................2.15 Source: http://www.yourgemologist.com/Charts%20and%20Graphs/coloredgemweights.html Note: you can incorporate the constants in the diamond estimation table for emerald, pear and marquise to get a better estimate for those here

The x times the thing a ma jig multiplied by... gosh this stuff is hard math was never my strong suit SPY

Now, now, now. Don't get excited . . . it's only arithmetic! Let me know if you need extra help! LOL!

It is if you have an appropriate scale, and the stone is unset and you are interested in the weight of the stone, itself, instead of an equivalent [eg CZ to diamond, CZ to sapphire, etc.] in which case you'd have to take the ratio of the specific gravities and then apply it to estimate the weight of the stone you are trying to mimic after you weigh the one you have.

Sometimes I set a stone from a parcel and forget to weigh it first. I sure do not want to take it back out to put it on the scale so I open the program on my computer called GT Pro. There is a space to type in the variety, the size and even more details then it will tell me the weight within about 10% accuracy. Very handy for set stones. It is also extremely handy for research on gems, cost less than a Franklin for the download and is fun to read too. Best regards, Lee

Lee-interesting you mentioned 10% + or -, I just had a pendent appraised & I know the weight of the stones was 25+ct. total. My appraiser basically used the chart & sure enough the weight is @ 9% less than actual weight. In the scheme of things I dont sell but do want to know approximate value & stone correctness to people who ask about the items I show as such & such. It is a useful tool, but should be used carefully-steve...

The original post is very handy information and I used it with classes by the school that is credited for it below the chart. Since I put GTpro on my computer, which I am sure uses the same info as in the charts, I find it easier to just type in a little info and the answer comes up magically. Robert teaches this information because many of his students become appraisers and will be looking at mounted stones. Best regards, Lee