Sunday, December 31, 2006

Gemstones ROCK!

A while back I mentioned that I was taking a class in gemstones. It's an earth sciences class, one of the GERs (general education requirements) required for my bachelor's degree. I've always liked rocks, so when I saw this class offered it seemed like a no-brainer. I knew I'd enjoy it, but I didn't know it would be one of the BEST classes I'd ever taken! I learned a lot, and I had FUN doing it.

I think that one of the biggest reasons I enjoyed the class so much is my professor. She had so much knowledge and enthusiasm to share with us you almost couldn't not "catch the fever". She went above and beyond the call of duty, always available to answer any questions, staying after class with a few of us interested in learning more, and sharing with all of us TONS of her own minerals, gemstones and jewelry. So, for all she has done, for all of her students and me personally, I'd like to take this opportunity to publicly thank Dr. Lori Dickson. Lori renewed my own personal interest in minerals, cultured my new interest in gemstones, and gave me the opportunity to spend lots of my hard earned money on yet another collection to be persued, enjoyed and shared with family and friends, and with you, the anonymous readership of my humble blog. Thank you, Lori!

Now, on the the FUN stuff: GEMSTONES!




This is part my latest purchase: 200 carats of rare and not-so-rare faceted gems. Amethyst, citrine, ruby, smokey quartz, garnet, sapphire, aquamarine, topaz, chrome diopside, labradorite, spinel, etc. Most people never get the chance to take a close look at all the various types gemstones, and it really a shame. They all have a unique kind of beauty. These gems formed in the ground hundreds of millions of years ago, before life ever spawned on earth. They've been lying there all this time just waiting to be discovered. Would you ever think that such beauty could be lying around in the dirt in your back yard?






Here's the rest of my latest purchase: 500 carats of cabochon gemstones. Most of them I haven't identified yet, but the tiger's eye and labradorite are easy to spot.








There's the labradorite.








Moonstone?








Here's one of my best! A blue star saphire.





I'm still not sure what this stone is. The colorless streaks make it a mystery to me. Anyone with a suggestion feel free to leave a comment.





Opals!!! There's FIRE in them thare stones! These are actually opal triplets. They have a layer of opal sandwiched between layers of other material, usually other minerals or plastics. This makes them more durable and probably helps keep them from drying out. Does that surprise you? It surprised me. Read on...


Long ago, before my gemstone awakening, I thought opals were organic, like pearls. Now I know they're not. Well, they kinda are, but they're different. Pearls are formed in oysters and muscles from nacre (or Mother of Pearl) secreted by the host. They contain water, calcium carbonate and some organic material. Opal is hydrous silicon dioxide that forms in cavities in the ground. Unlike most gemstones, neither pearl nor opal are minerals. The presence of water and the lack of a crystalline structure make them mineraloids. It's the water along with the alignment of silicon spheres that gives opal it's distinctive optical properties, or play of colors.





There are many identifying characteristics of gemstones, one of which is it's density, or specific gravity. Above is my rig for measuring specific gravity. You weigh the stone 'dry' (the easy part) then weigh it under water, or 'wet' (the hard part). The difference between the two wieghts is the weight of the water the stone displaces. The ratio of the dry weight to the water's weight is the specific gravity.


I'm very proud of this rig. I think MacGuyver would be proud, too. It was fun making it. Wanna make your own? Here's how:

Parts list:

  • Digital scale with 0.002 grams (min) resolution - the more sensitive the better.
  • Extraneous wire coat hanger.
  • Bottle of good (or bad) beer (actually, only the bottle cap is required).
  • 6" length of flush chain from toilet tank repair kit.
  • Razor blade.
  • Vice-like device to hold razor blade.
  • Cup, small jar or equivalent to hold water.
  • Small dead weight (live weights move around too much!).
  • String or dental floss.

Tool list:

  • Linesman pliers (or equivalent) sufficient to cut coat hanger.
  • Hammer.
  • Small cold chisel.
  • Needle nose pliers.
  • Electric drill.
  • 0.060" drill bit.
  • Blocks of various height.
  • The obligatory tube sock.

Assembly instructions:

  • Open bottle of beer being carefull as to not excessively mutilate the bottle cap.
  • Drink bottle of beer. DO NOT GUZZLE the beer! Take the time to enjoy it.
  • Wash bottle cap.
  • Using the electric drill and 0.060" drill bit, install three equally spaced holes in the peripherie of bottle cap. These holes will be used to suspend the bottle cap from the balance beam
  • Cut coat hanger as necessary to produce about 8 inches of straight 'balance beam".
  • Bend a "V" hook in the right end (for suspending the bottle cap).
  • Secure the razor blade in the vise-like device - This will be the fulcrum for the balance beam.
  • Arrange the scale, vise-like device and water container at the appropriate heights. Try to arrange the elements such that the fulcrum is closer to the scale than it is to the water container. The idea is to create an exaggerated weight measurement that will reduce any errors indroduced by air bubbles clinging to the stone and swaying movements of the underwater platform. Don't worry, the calibration process will ensure you get accurate results.
  • Using the cold chisel and hammer, make a "registration mark" within 1 inch from the left end. This will align the dead weight in a fixed location.
  • Using the cold chisel and hammer, make another registration mark at the appropriate distance from the first registration mark. This will be used to balance the beam on the razor blade "fulcrum". Make the mark on the bottom of the beam, so that when you orient the "V" hook in the upright position the registration mark will be able to engage the razor blade fulcrum.
  • Using the appropriate length of string or dental floss, secure the dead weight to the beam at the left registration mark such that it will rest on the scale when the beam is resting in a horizontal orientation.
  • Place the beam on the fulcrum engaging the fulcrum and bottom registration mark with the dead weight resting on the scale.
  • Using the needle nose pliers, assemble lengths of chain appropriate for suspending the bottle cap from the "V" hook into the container of water. HINT: You may want to use string or dental floss for suspending the bottle cap. I suspect the water's surface tension along the links of chain will be enough to influence your measurements. In my final design, I replaced the three lengths of chain that extend below the water line with dental floss and found the measurements to be more consistent.
  • Fill water container with water such that bottle cap is submerged.

Congratulations! Your specific gravity machine is complete. All that's left is the calibration process:

  • Remove the water container and any water left in the bottle cap.
  • Gently move the dead weight off the scale so that you can weigh a gemstone normally.
  • Using only the scale, weigh a gemstone that is typical for your collection. Record the weight.
  • Repeat this for a total of ten weights. They should all be within the limit of your scale's resolution. My scale has a resolution of 0.002 grams, so all weights are +/- 0.002 grams.
  • Average all weights. This will be the normal "dry" weight.
  • Replace the dead weight on the scale.
  • Turn on the scale and zero it.
  • Place the gemstone in the bottle cap. The scale should display it's NEGATIVE weight. because of the design of the beam, this weight will be exaggerated. Record it.
  • Remove the stone and allow the scale to return to zero.
  • Weigh the stone again. Record the weight. Do this a total of TEN TIMES.
  • Your recorded weights should all be very close to each other. Any reading(s) that seem way out of place should be re-done.
  • Average all ten readings.
  • Divide the average by the "dry" weight of the stone. This will be your rig's scale factor. Write it down and don't lose it. ALL WIGHT MEASUREMENTS WILL NEED TO BE DIVIDED BY THIS SCALE FACTOR.
  • If you want to get really picky, you should know that specific gravity is referenced on the weight of fresh water at 4 degrees centegrade. Like me, you will probably be using regular old tap water at room temperature. How much difference does it make? I did some research. The answer is, "not much." However, if you're like me, you'll want to minimize as much error as possible. You can compensate for the less-dense-ness of tap water. After you calculate the weight of the displayed water, simply multiply it by 1.00177. Near as I can tell, that's about the best we're gonna get. I'll leave the exact specific gravity formula for you to deduce. You have all the information you need.

So, that's about it. If you're smart - and if you've read this much you probably are - you'll weight all your gemstones dry first, then assemble the specific gravity rig and make all your wet measurements, then enter all your data into your spreadsheet. Did I mention that you'll need a spreadsheet to make all the calculations? Well, you don't actually need one, but it sure helps.

Have fun!



That's all for now. I'm sure I'll find a lot more to write about later. Happy new year!



posted by The Czar at Sunday, December 31, 2006 0 comments links to this post