Image 1

Specific Gravity Kit for your Carat Scale

2.00 LBS
  • Product Description

    An Electronic Scale can be used to measure the specific gravity of gemstones.  As with most hydrostatic devices, you simply weigh the stone "in air" and then weigh it in water.  A typical scale intended for such purpose has a "weigh below" hook on the underside of the scale from which to suspend a "gem holder" in a container of water.  While this works for a weighing of the stone in water, it is an awkward operation - the scale must be elevated on a stack of books or the like, and the user must work in a confined space underneath it.

    Mineralab has, instead, developed a very user-friendly "above the scale" underwater weighing process, along with a Universal Specific Gravity Kit (see photo above).  Just weigh the stone "in air" on the integrated weighing platform of the scale, then without changing any setup, weigh the stone in water by placing it in the underwater weighing pan of the gem holder suspended above the platform.  Then plug those two values into the Specific Gravity equation to obtain the specific gravity of your stone.  It's that easy and it takes only a few seconds!  See our YouTube video below:

    The photo above shows the components of our Universal Specific Gravity Kit, and how it is utilized with an Electronic Scale.  A beaker of water sits within a spill-resistant support independent of the scale itself, while a lightweight gem holder rests on the scale's weighing platform, with the weighing pan suspended underwater.  The components of our Specific Gravity Kit include the following:  

      Lightweight Gem Holder Support and Underwater Weighing Pan
      Independent, Spill-Resistant, Adjustable Beaker Support
      Beaker for filling with water - 50ml capacity, with approximately a 1.6" inside diameter.
      Aluminum Test Weight whose SG = 2.70
      Stainless Steel Tweezers
      Complete instructions (although this method is very simple)
      Table of 100 common gems sorted by specific gravity, with 6 other properties, including refractive index.  (Or purchase our Mineral Search software and let your computer do the work of searching a gemstone database by specific gravity and other properties)

    We developed this particular version of our Universal Specific Gravity Kit primarily for the gem and jewelry trade, and in doing so, we downsized the components to be compatible with virtually any pocket/compact Carat scale, provided that: 

    • The scale has a minimum capacity of 50 carats.
    • The scale has a tare (re-zeroing) function.
    • The scale's weighing platform is large enough to accommodate the 1.75" diameter base of the kit's Underwater Weighing Pan Assembly.
    • If the scale has a draft shield or lid, it must be either removable, or hinge back away from the scale.


    • FYI, the "tared weight" of that portion of the kit that sits on the weighing platform is about 40 carats, so this must be subtracted from your scale's listed capacity to derive available capacity for specific gravity measurements.
    • FYI, this downsized kit includes a compound plastic base, including a U-shaped section on which you place your Carat scale.


    For those who need accurate specific gravity measurements on small, lightweight gemstones, these further criteria are necessary:

    • The weight range of the scale should accommodate specimens as light as possible, say with a Readability down to .005 to .01 carats.  Refer to this Sensitivity Table for details on how accurate and sensitive a particular scale will be for specific gravity measurements
    • The scale should provide for calibration, either internally or through the use of calibration masses.
    • The scale should ideally offer readout in carats, in addition to grams.


    This item typically ships within 1 business day.

  • Product Reviews


    Write A Review

    1. Muy Buen Producto y el envio es rapido (Very Good Product and shipping is fast)

      Es un producto de calidad, el envío se demoro solo 3 semana a Chile, así que estoy muy contento por mi compra

      (It is a quality product, the shipping took only 3 weeks to Chile, so I am very happy with my purchase)
      on Jun 17th 2021

    2. I recommend

      Excellent on Apr 6th 2021

    3. Specific Gravity Kit

      Fantastic piece of equipment which has already help solve a few mysteries and confirm others. on Mar 16th 2021

    4. Specific Gravity Scale

      Excellent piece of equipment. Very useful and practical. It has helped me tremendously. Glad I bought it. on May 26th 2020

    5. Pretty Simple but cool

      The set up is easy enough to understand but, when you read the instructions, for how to calculate the specific gravity, they left out a step. Once you measure dry, then in water, and subtract the water weight from the dry weight, that is where their explanation ends but, after that, you are supposed to take, the water weight and divide it by the number you got, subtracting the water from air weight. And that, is your specific gravity weight. But once I found that out, it was super easy to use, and pretty damn accurate, if you follow instructions exactly. on May 24th 2020

    6. Parfait

      Parfait. Article conforme, livraison rapide, documentation fournie.

      (Perfect. Compliant item, fast delivery, documentation provided.)
      on Mar 20th 2020

    7. Great Tool

      Well packed, items arrived undamaged, easy to setup, which helps in hitting the ground running and collating all the SG data. on Oct 21st 2019

    8. Perfect for measurements

      System is perfect for measurements on Sep 25th 2019

    9. Fast Shipment

      Great product, fits perfectly with my scales. Was very impressed with the fast shipping to Australia. One thing I think would improve would be if it came with a storage bag to protect it when not in use. Highly recommended Mineralab for service. on Aug 15th 2019

    10. Helps determine precious metals and stones

      A must-have tool for jewelers! (unless you're a real fan of testing metals with acids.)
      Helps distinguish between most common gold, silver, and platinum alloys. No toxic chemicals or scratching needed (as opposed to testing with acids). Cost-efficient (no need to buy expensive Gemoro pens). No more guesswork when a customer asks you to resize a ring they brought from an exotic vacation.
      So far, I've tested it with:
      - 24k gold (SG around 19)
      - 18k yellow gold (SG ~15)
      - 14k yellow gold (SG ~13)
      Haven't tested white gold yet, but would predict that zinc/nickel alloys would be just a bit lower than yellow gold, and palladium-based alloys just a bit higher/denser.
      - sterling silver 925 (SG around 10)
      - platinum 950 (SG ~19-20, iridium-based alloys higher ~20-21)
      And of course, it helps you determine gemstones, but better use it in conjunction with a spectroscope, filters, and a microscope (or loupe).
      on Feb 4th 2019

    11. Works Great!

      Exactly what I wanted, well crafted and light so you have more capacity in what you want to identify. Compact size but allows me to ID some of that unknown or mislabeled facet rough. on Apr 16th 2018

    12. Great

      Very very happy! 180€ in France 96 with you shippemend included. Very good material! on Feb 7th 2018

    13. Great product

      This item is exactly what I wanted. I have a small desk space and I needed an accurate SG kit to fit the space. It was easy to set and has proved to be reliable and accurate on Jul 21st 2017

  • Find Similar Products by Category