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 Post subject: Thread moved. Geezers arguing
PostPosted: Thu Nov 07, 2013 4:49 pm 
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I have started a new thread since Dr. Bill and I sort of hijacked the one about "building a refractometer" for which apologies.


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I respectfully disagree with Dr. Bill. I think a microscope is useful even for identification. ... No less a gemmologist than Basil Anderson referred to the microscope as one of the legs of the tripod of gemmology.

One must remember, Gemmology, as he used the term, is far different from simple gem identification.


I am not sure about that. Perhaps you could clarify exactly what you mean. In my opinion the microscope is quite useful. Many gemstones have characteristic inclusions that are easy to spot with the microscope and are diagnostic. Some very famous gemologists have made major careers using mainly the microscope and microscope camera. I think if you polled gemologists you would find that the great majority of them like their microscopes and they would not give them up.

I have had the occasion to teach microscopy to several high powered MDs, and to some other scientists, too. My observation is, that one needs to develop certain microscopy habits hopefully early in ones use of the scope. Sometime people fail to develop these habits , because nobody taught them correctly and they end up hating the microscope. No scientist nor gemologist should ever hate the microscope. I feel like you do Bill.
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After all, Basil even used and recommended a microscope for mounting his spectroscopy studies.


In the early part of the twentieth century the microscope and the (hand) spectroscope were made for each other. Both Zeiss and Beck of England built microspectroscopes. Basil Anderson essentially copied those and E. Gubelin did too. After a brief hiatus of working apart the two instruments are together again with micrscopes mated to FTIR and Raman instrumentation. Undoubtedly a match made in heaven. Isn't one of the gadgets I got from you a sleeve intended for slipping an OPL into a gemscope? (it didn't fit)

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On the other hand, Gem Identification uses NUMBERS, and as Lord Kelvin said, "Without numbers, one's knowledge of a material is of a meager and unsatisfactory kind." Microscopes do not produce numbers.

I am quite familiar with Lord K's famous quotation. But actually it is not one of his better ones. It actually means nothing.
There are many kinds of knowledge. The color of a gemstone is of great taxonomic value but is not a number. The size and shape of characteristic inclusions are not numbers. The surface luster as normally described (not the LH value) are not numbers. The cleavage is not a number. The crystal habit is not a number. But they are definite knowledge and are data points in the algorithm for Gem ID. The taste, and smell are not numbers. The streak is not a number. The heft is not a number (though related strongly to SG)

The Hodgkinson method does not really produce numbers. If someone is very skilled it may produce estimates. and estimates of ratios.



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If you want to buy a spectroscope buy an OPL. ... Dr. Bill used to carry those and I think Barbra may too.
As a matter of fact, Basil introduced me to the OPL and I purchased them from Colin Winter. I introduced them to the GIA and was their original source of supply.

So what actually happened between you and the GIA?? They used to sell your books too.


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I also have a large collection of reflectometers including two of yours. They are largely a disappointment to me. (reflectometers generally, yours are neither better, nor worse, than the others.
If something happened, that required me to keep only one reflectometer, I probably would select The Jeweler's Eye)

Would that choice be based on the quality of instrument or the fact all other instruments have fictitious scales for RI which give the wrong answer as they do not factor in dispersion,

No , The Presidium also has an arbitrary numerical scale which is correlated to the value obtained for different stones. But it is digital.

The reason I like yours is that it has an analog meter.
I like the Diamond Eye because it is CHEAP. Priced about what these things should be priced and a somewhat narrowed range too.

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or the fact my instrument produces a numerical value for luster of the facet, which has no relationship to RI but is useful for gem ID

I have not found the L sub H value to be particularly useful nor any reflectometer to be repeatable enough for routine gemological use. I have four or five different models and have examined sometimes in detail a couple of others too, as well as having corresponded with a few people (mostly listmembers here) about the merits or lack thereof of yet other models.

If you want to measure reflected light from a gemstone at the very least you need to use techniques like this guy uses.
http://jm-derochette.be/Spectrometer/Photometer1.htm
http://jm-derochette.be/Spectrometer/me ... ection.htm

That includes yellow light like a sodium lamp and a sensitive detector and the ability to make sure you arent't getting retroreflection from the pavilion of the stone.


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I wonder if you have a functioning sodium light in your collection Bill.
If truth be known, I got rid of my sodium light back in 1978. When I had finished my work on luster and adopted the Hodgkinson method for RI, birefringence, and dispersion, the critical angle refractometer was of no more interest to me.


Well in my opinion you might have thrown the baby out with the bath water.
I eagerly awaited, and cut out, and saved, the three part article on the Hodgkinson method that you published in Lapidary Journal.(the 1980s iirc?) I have taken the day long course from Alan when he taught it in Houston a few years ago. I have his original book and his video tape and have eagerly sought to soak up everything I can find on the subject.

Yet I think the method or methodology is a bit incomplete. The Gemology Project mentions it. But if I had to choose between a refractometer and the Visual Optics method I would not want relinquish my refractometer.
You and Alan might be the only people on the planet who can really use it. It does not require instruments, but it does require remembering the dispersion and birefringence and maybe the RI of any stones you care to ID. That is why God made Gemology Tools Professional :D




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Are you trying to say the GIA is not concerned with profit?

Even a non profit organization has to keep the lights on. I think GIA makes enough money on their Diamond Grading activities that they ought to give away both courses and instrumentation too.
But I don't think they viewed the Gem Instruments division as a profit center. If they were making profits on the instruments they would not have trimmed their catalog of instrumentation down to almost nothing. They would have kept on selling them.

Their prices are a bit high and always have been. I myself delayed getting very serious about gemology until the advent of ebay and the ability to buy used instruments at a fair price.
But if I had it to do over I would have just bitten the bullet and bought the suite of GIA instrumentation. (in about 1972) It is to routine gemology, what Steinway is to pianos.


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Let me tell you about that void.
The void occurred when Basil Anderson died in 1985. In the teaching of gemology (GIA/GAGB or GemA), there was no one to take his place because either no one knew enough or cared enough. Effectively, the teaching of the classical fundamentals of gem testing progressed no further.

Well we certainly lost a giant when BA passed away, but he was not the only one out there. I think that statement is a bit disrespectful to many others. Including you.




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Still today, no one is teaching anything newer than 1980, probably, because their teacher's were never taught anything new
.
I don't really agree with that either.

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That is because there has never been a "good" book about gem testing since Anderson's 9th edition in 1980. Later editions of B. Anderson and R. Webster books have been revised and those authors essentially ruined their values because they didn't know enough to properly evaluate the more recent approaches which they touted.

The latest copy of "Gems etc." By Webster that I have is the fifth edition edited by Peter Read and I find it just fine. I have heard that the sixth edition has trimmed a bunch of stuff that perhaps should not have been but I have not seen it.

I have the tenth edition of Gem Testing and it looks about the same as the much earlier edition I have also.

What more recent approaches are you referring to?

With high speed internet now neither GIA nor GAGB nor anyone else has a monopoly on gemological knowledge and new findings disseminate and propagate very fast. GIA has made Gems and Gemology available for free online. What more could one ask for?? It is also probably just a matter of time before someone puts together a MOOC on gemology (Massively Open Online Course)


Last edited by G4Lab on Fri Nov 08, 2013 12:44 pm, edited 1 time in total.

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 Post subject: Re: Thread moved. Geezers arguing
PostPosted: Thu Nov 07, 2013 5:59 pm 
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The color of a gemstone is of great taxonomic value but is not a number.

You need to expand your concept of number and measurement. For example, color is a number. By custom, we give that number (or trio of numbers, usually) a name like red, blue or fuchsia, but it is no less a quality with a measure.


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 Post subject: Re: Thread moved. Geezers arguing
PostPosted: Thu Nov 07, 2013 6:32 pm 
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I am familiar with the various color measurement schemata. They follow from the fact that we have red green and blue detectors in our retinas. They are not the kind of numbers Lord Kelvin(or if I understand him Dr. Bill too) was talking about. Mapping physiological sensations to numbers is not the same as measuring mass or specific gravity or refractive index or many other straight forward numerically denominated qualities. Color itself has no dimensions although most of the measurement systems have multiple dimensions.


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 Post subject: Re: Thread moved. Geezers arguing
PostPosted: Thu Nov 07, 2013 8:19 pm 
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G4Lab wrote:
Color itself has no dimensions

One dimension. Nanometers is the usual unit.

And I think Lord Kelvin knew exactly what he meant.


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 Post subject: Re: Thread moved. Geezers arguing
PostPosted: Fri Nov 08, 2013 12:30 pm 
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Nanometers is measure of length not color. I presume you mean the wavelength of light which is not the same thing as color at all.

Lord Kelvin misspoke often enough that his wiki page has a section on stuff he said that was wrong.
http://en.wikipedia.org/wiki/William_Th ... o_be_false

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Pronouncements later proven to be false[edit]

Like many scientists, he did make some mistakes in predicting the future of technology.
Circa 1896, Lord Kelvin was initially sceptical of X-rays, and regarded their announcement as a hoax.[54] However, this was before he saw Röntgen's evidence, after which he accepted the idea, and even had his own hand X-rayed in May 1896.[55]
His forecast for practical aviation was negative. In 1896 he refused an invitation to join the Aeronautical Society, writing that "I have not the smallest molecule of faith in aerial navigation other than ballooning or of expectation of good results from any of the trials we hear of."[56] And in a 1902 newspaper interview he predicted that "No balloon and no aeroplane will ever be practically successful."[57]
The statement "There is nothing new to be discovered in physics now. All that remains is more and more precise measurement" is given in a number of sources, but without citation. It is reputed to be Kelvin's remark made in an address to the British Association for the Advancement of Science (1900). It is often found quoted without any footnote giving the source.[58] However, another author reports in a footnote that his search to document the quote failed to find any direct evidence supporting it.[59] Very similar statements have been attributed to other physicists contemporary to Kelvin.[60][61]
In 1898, Kelvin predicted that only 400 years of oxygen supply remained on the planet, due to the rate of burning combustibles.[62][63] In his calculation, Kelvin assumed that photosynthesis was the only source of free oxygen; he did not know all of the components of the oxygen cycle. He could not even have known all of the sources of photosynthesis: for example the cyanobacterium Prochlorococcus—which accounts for more than half of marine photosynthesis—was not discovered until 1986.

I do sometimes agree with that quotation but it does not apply everywhere. It is also arrogant , conceited and paternalistic. As though he is the arbiter of that which is correct and not correct. Big shot scientists and politicians and wealthy people often fall into this trap. Look at Linus Pauling.
Won two Nobels and persisted in fomenting theories that have been soundly ,consistently and repeatedly disproven, when carefully examined using the scientific method. He seriously damaged his reputation because HE knew better.

I suggest you read the book "Thing Knowledge, A Philosopy of Scientific Instruments"

http://www.amazon.com/Thing-Knowledge-P ... 0520232496

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Book Description
Publication Date: February 10, 2004 | ISBN-10: 0520232496 | ISBN-13: 978-0520232495 | Edition: 1
Western philosophers have traditionally concentrated on theory as the means for expressing knowledge about a variety of phenomena. This absorbing book challenges this fundamental notion by showing how objects themselves, specifically scientific instruments, can express knowledge. As he considers numerous intriguing examples, Davis Baird gives us the tools to "read" the material products of science and technology and to understand their place in culture. Making a provocative and original challenge to our conception of knowledge itself, Thing Knowledge demands that we take a new look at theories of science and technology, knowledge, progress, and change. Baird considers a wide range of instruments, including Faraday's first electric motor, eighteenth-century mechanical models of the solar system, the cyclotron, various instruments developed by analytical chemists between 1930 and 1960, spectrometers, and more.


Davis Baird grew up in house constantly visited by eminent scientists. His father was one of the founders of Baird Atomic a firm which developed early rounds of atomic emission spectrometers.(what is referred to in the last sentence above.) He rubbed shoulders with some real immortals but chose to go into that most non-numeric of pursuits, philosophy.

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 108wt_1125
Above is an advert somebody is trying to peddle on ebay for one of their scanning spectrofluorimeters that have two double monochromators. Really really advanced instrumentation for its day.

Finally , I do spend a significant percentage of my working time adjusting and calibrating scientific instrumentation so that the numbers they output are correct. I have both at work and in my personal collection a large number of calibration standards for a very wide variety of quantities. (Including a very large selection of wavelength standards of many different types[reflection, transmission/absorbance and emission] , and many items that were calibrated trace-ably to NIST and in a couple of cases BY NIST )
So I don't think I need anyone to lecture me about Lord Kelvin's 150 year old quip. Are you seriously proposing that a microscope is not useful for gem identification????


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