A Multipurpose Microscope Stage for Gems


When observing gemstones through a microscope, it is normal to use gemological tweezers. These tweezers can be attached to the microscope itself or to an external support. While it is important to use tweezers instead of your fingers because your fingers can leave dirt, oil, and fingerprints behind, making minor movements and adjusting to different angles can be difficult or limited. This is mainly because the gemologist has to move the tweezers by hand and the movements are enlarged by the microscope, making the image jump in abrupt movements. Rotating the gem is also not easy because the small button of the tweezers does not allow for soft movements.

To solve this problem, we conceived a multipurpose microscope stage for gems, which can be seen in Figure 1. You can see how this microscope moves in the video below.

Figure 1
Figure 1: A multipurpose microscope stage for gems.

To build this you will need:

  • A cheap microscope stage
  • A telescope counterweight or other type of support
  • A telescope focusing pinion (see Figure 2)
  • A large plastic or metal gear
  • Gemological tweezers for microscope
  • An aluminium rod (square or round profile) 7.5 cm (3 inches) in length
  • Some nuts and bolts, Nural 21 or any good epoxy glue
  • An old radio antenna
  • 3 or 4 thin rubber legs

The counterweight and the focusing pinion can be found at a telescope shop, a scrapyard, or from an old telescope that you can mine for parts. The counterweight we used had a 1.3 kg (2.2 pounds) weight.

Let’s talk about the microscope stage. Those devices can cost you thousands, depending on the quality. Some devices are very sturdy, having several degrees of liberty. You can move the piece up and down, left to right, closer or farther away, and all these movements can be done with a fast motion and slow motion knob. But you need none of this. Just buy a simple, cheap stage like the one that you can see in Figure 2 (this one cost us US$25 on Ebay).

Figure 2
Figure 2: Telescope focusing pinion

With this model you have two possible movements: forward and back, left to right. This tool is made of metal, with the exception of the plastic knobs and the interior gear stripe. Because the gear stripe is plastic, use care when using and do not force the mechanism.

First, remove the pieces marked with the arrows that you see in Figure 2. You may want to hold on to these parts for future use. Remove the left piece, but keep its base and put the screws back in place. Remove the two pieces on the right side. They have a small spring. Put all this aside, but KEEP the main screw because it be will needed later on. Remember to remove just the indicated pieces. Put the small screws back to their places. Tighten up all the screws of the stage.

Now, get the telescope focusing device and prepare it (See Figure 3).

Figure 3
Figure 3: This diagram shows how to prepare the telescope focusing device.

To prepare the telescope focusing device, remove one of the knobs. You can do this by either cutting or heating the metal. If you use heat, remember to do it with care, because you will need at least one of these plastic knobs. We prefer to heat than to cut in order to retain a longer rod. Leave the gear in place or move it slightly (approx. 1-2 mm) from the remaining button.

Now, prepare the tweezers. Look at Figure 4 for a detailed look at how to do this.

Figure 4
Figure 4: This illustration shows how to prepare the tweezers.

The great gear is a large plastic gear recovered from scrap. This gear will interact with that small gear that you have in the prepared focusing device. So find a large one with five or six times more gear teeth than the small one. We used a 6:1 relation for our device. This means that the small gear has 16 gear teeth and the large one has 96. To use these two gears, we need to turn the knob 6 times to obtain 1 complete turn of the great gear (a slow motion). Try to compose the pieces before any drill or cut. When you are sure about the dimensions and placement, cut a piece of an old antenna, or any other tube you prefer, and insert it in the tweezers. This will function as a stopper. Insert the great gear and measure where you will drill a passage for a small screw. Ensure that the small screw can firmly secure the great gear.

Now, to finish this part of the job, use a metal U-shaped form to join the parts. The focusing knob will pass through a hole, in a way that the two gears can interact together. Use another small tube to convey the axis of the focusing knob, make a screw thread in the free end, and close it with a screw-nut. We also use a small spring and a receiver to stabilize the system. To secure this part to the stage, you will use the original screw that was removed and saved. See Figure 5.

Figure 5
Figure 5: Our completed microscope stage.

The last thing you need to do is make the support base. This step is quite simple. First, make a threaded hole on the top. Cut the rod according to your needs, keeping in mind that the length will depend on the height of your microscope. Do the cut in a way that when the rod is inserted in the telescope counterweight you could pull or push the rod to some extent and use a good screw attached to a plastic or metal button. With this, secure the stage to the top of the rod, insert the rod in counterweight center hole, and complete the job by gluing the rubber legs on the bottom of the counterweight. See Figure 6.

Figure 6
Figure 6: This photo shows the support base.

In the following photos, you can see how handy this stage can be. These photos required less than 30 seconds. They would have taken much more time without our multipurpose microscope stage.

Spinel
A photograph of spinel from the table.
Spinel 20X
A photo of the same spinel at 20x magnification.
Spinel 40x
A photo of the same spinel at 40x magnification.

About the author
Dr. Raul Berenguel, PhD.
Dr. Raul Berenguel, PhD. holds a degree in History (Scientific Branch) from Universidade de Aberta (2008), having obtained a PhD in Contemporary Art (2012), in the specialty of Contemporary Art (specifically in Gemology), at the same university. He has specific expertise in history, gemology and contemporary art, and the application of the traditional technical means of gemology in the gemological investigation applied to objects of art.
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