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  • “There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self.” Ernest Hemmingway
  • “Judge each day not by the harvest you reap, but by the seeds you plant.” Robert Louis Stevenson
  • “We must be the change we wish to see in the world.” Gandhi
  • “Noble deeds that are concealed are most esteemed.” Blaise Pascal
  • “A creative man is motivated by the desire to achieve, not by the desire to beat others.” Ayn Rand
  • “If you want to succeed you should strike out on new paths, rather than travel the worn paths of accepted success.” John D. Rockefeller
  • “Honesty is the first chapter in the book of wisdom.” Thomas Jefferson
  • “Sense shines with a double luster when it is set in humility. An able yet humble man is a jewel worth a kingdom.” William Penn
  • “There is a great satisfaction in building good tools for other people to use.” Freeman Dyson
  • “You don't know what you can learn until you try to learn.” Ronald Coase
  • “Let us so live that when we come to die even the undertaker will be sorry.” Mark Twain
  • “Create more value than you capture.” Tim O'Reilly

Specific Gravity Calculator for Gemstones

A gemologist friend of mine recently complained about the tedium of calculating gemstone and mineral specimen specific gravity via the hydrostatic weighing method. You see, after weighing the specimen in air (at room temperature) and in water (at 4º Celsius, ideally) one must do a little math to determine the specific gravity (S.G.) of a sample. The formula is very simple: It’s the weight in air, divided by the loss of weight in water (at 4º Celsius). Or: the weight in air, divided by the weight in air minus the weight in water. Simple. Right? But when you do dozens (or more) of these a day, it gets tedious. High-end lab equipment will do the calculations for the technician, but my friend doesn’t have such equipment. And such equipment doesn’t help if one is in the field.

There are a few calculators on the Web, but most are not mobile-phone-friendly, and he likes to use his iPhone around his lab. So I coded this simple little web app to help my friend in his time of need. Of course he wants a native iOS app, but that seems a bit overkill for such a simple task.

Now I just need to update this site to modernize it and make it mobile-friendly. So little time…

If you’d like to use the calculator, you can go here and calculate ‘til your heart’s content. It’s labeled to suggest entering carat weight (for precision), but entering weight in grams is fine as well (but rounding may negatively affect accuracy, depending upon your precision). Most important is to not mix units of measure. end of article icon

Posted on Saturday, May 16, 2015 in Technology • Everything Else •

Comments

1. Posted by James on May 17, 2015

Thanks for doing this, Dale! It works great on my iPhone 6 and just what I needed. As you know, Metler offers a solution with their high-end balance and hydrostatic kit that automates the process, but that’s overkill for me right now.

2. Posted by Dale Allyn on May 17, 2015

Hey, James, you’re welcome, of course. It’s nothing fancy, but hopefully it’ll be handy for you.

Yes, the Metler JP series is quite nice with the hydrostatic kits, but it’s a bit costly if you don’t need the whole thing.

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