Post subject: W. Wm Hanneman Instrument Donations to our GO Members
Posted: Tue Feb 19, 2019 3:48 pm
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
I will be listing several instruments Dr. Hanneman has donated to our platform. Everyone will be welcome to take advantage of this generous offer.
We will also encourage discussion of how each tool works and how it can be beneficial to those both on a limited budget and those who like to understand the science behind the instrument
Post subject: Re: W. Wm Hanneman Instrument Donations to our GO Members
Posted: Tue Feb 19, 2019 11:40 pm
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Our first tool available is "The Magnetic Wand" Synthetic Diamond Detector
Originally designed to detect synthetic diamonds, it can also be used in concert with the research done by Kirk Feral. The magnetic wand is composed of a small but powerful magnet mounted on a wooden rod. The magnet itself is composed of neodymium iron-boron and is claimed to be the most compact magnetic material available. It will lift a weight of nearly 1 pound. A protective case is also provided for storage in order to reduce the magnet's magnetic field.
Post subject: Re: W. Wm Hanneman Instrument Donations to our GO Members
Posted: Wed Feb 20, 2019 6:59 pm
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Item #2I HAVE SEVERAL ! Dr. Hanneman's Coniscope
In gemology, we use a conoscope (a strain free acrylic or glass sphere on a rod) to determine optic character (uniaxial or biaxial) in anisotropic gemstones. The conoscope creates a 2-dimensional image of the 3-dimensional interference in a mineral. Although determining the optic character with a conoscope is a fairly easy procedure, finding the interference figure itself is not. The interference figures always appear around the optic axes of minerals.
The simplest way to find an interference figure is to rotate the stone under the polariscope, in every possible direction, while looking down the analyzer until one sees a small flash of colors appear on the surface of the gemstone. When that flash of colors is found, fix the stone in that position and hover your conoscope slightly over it. Now, while still looking through the analyzer, you should see the color flash transform into a rounded 2-dimensional image. This image in uniaxial stones will appear different from the image in biaxial stones, each having its own characteristic pattern.
Using an immersion cell along with the polariscope may enable you to find the flash figures more rapidly.
Due to enantiomorphism , quartz will give a typical uniaxial image but with a large "target" in the middle. That is what is named a "bull's eye" and is typical for quartz (both natural and synthetic).
Because anisotropic minerals appear to be single refractive when viewed down the optic axis, another technique for finding the optic axis can be used. View the stone under the polariscope from all sides to find where the gemstone does not blink light and dark on lateral rotation. That will be the optic axis. Remember that uniaxial minerals have one optic axis while biaxial gemstones have two optical axes.
Post subject: Re: W. Wm Hanneman Instrument Donations to our GO Members
Posted: Thu Feb 21, 2019 12:56 pm
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Item #4 Dr. Hanneman's Toughness Tester for Jade
Dr. Hanneman wrote:
Way back in 1973 when SEMs (Scanning Electron Microscopes) were “new”. photographs were published in the American Mineralogist showing the matted structure of nephrite jade, the shingly structure of jadeite jade, and highly magnified views of other mineral surfaces. Also, in that article, quantitative data on what was called “fracture toughness” were reported.
On the basis of this information, I, in all my modesty, created what I christened the “Hanneman Relative Toughness Scale”. I hoped it would eventually become as famous as Mohs’ Scale—but it didn’t. That was because my name was attached to it, and the GIA never promotes techniques which were “not invented here”. Consequently, while the technique was published in Gems and Minerals, GIA students were never made aware of its existence.
Granted, the concept is not earth shaking, but it does go a long way in demonstrating why jadeite and nephrite are highly prized. Also, it is a concept that would require less than 5 minutes of class time to teach, and the student would remember it for life. Now for the test.
1. Take a small fragment of the test stone, about the size of a half grain of rice—small fragments of nephrite are provided in the kit. 2. Place the test stone between two hexagonal (bathroom tiles) streak plates—these are provided in the kit. 3. Reduce the fragment to a fine power by applying pressure and grinding the plates together with a circular motion. The results will be obvious.
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