[Jewelry making - Article 01125] - [Orchid] Gemological Microscope.

[Robert Powell]

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    I am making free use of partial articles and wish to thank these
    persons, listed and non listed for their contributions. Thank You
    very much.    -    ROBB    -    Robb  Powell . 

    I made my decisions to purchase my microscopes used at eBay . I did
    so after looking for 4 weeks, and shopping on eBay for another 4
    weeks I have written about my choices with purchasing a microscope 
    Here it is. 

    2 - Quantify - Reichert Stereo Star Zoom Microscopes Model 570 Zoom
    range 7x to 42x with WF 10x paired eyepieces Reichert-Jung
    articulated boom stand with focusing arm 

    2 - quantify - Part # 575: .5x Auxiliary objectives magnification
    range =3D 3.5x to 21x with 6" working distance 

    2  - QUANTIFY - VOPI INTRALUX 4000 HIGH INTENSITY FIBER OPTIC
    ILLUMINATORS RING MOUNTED TO AUXILARY SCREW IN 0.5 OBJECTIVE. 

    I purchased a duplicate microscope so that if I needed work done, I
    would not be without a spare microscope And as use as a dedicated
    gemological microscope. I purchased both microscopes 2 illuminators,
    1 boom stand and sundry other items from MIKE MATHIS  wsjcam AT aol.com
    I was well treated and can recommend this as a place to start
    looking. 

    "AO was bought up by Reichert-Jung and then they were bought by
    Cambridge Instruments. At some point, Leica bought up the AO
    microscope line along with the Bausch & Lomb line, and then shut down
    the AO line. There are lots of used microscope shops around that may
    have parts, but it's a bit hit or miss.  Apparently the B&L scopes
    were far more common, and are still being made under the Leica name.
    " 

    I am going to include my resources and information so everyone
    interested can make a choice. 

	Very good sites well recommended -
 	ABSOLUTE CLARITY & CALIBRATION, LLC       -    start here !
	109 Main Street  v Terryville,  CT  06786
	Phone (860) 583-0502 v FAX (860) 314-1851
 	http://www.absoluteclarity.com/buy&avoid.htm
 	http://www.absoluteclarity.com/buy&avoid.htm

    	And here    -     Nikon Microscopes -
    http://www.microscopyu.com/articles/stereomicroscopy/stereointro.html
     

    Also here    -    Meiji Microscopes offer a very good value at a
    very good price ... Meiji Microscopes -  http://www.meijitechno.com/ 

	Google Groups
	google group: sci . techniques . microscopy
	googol group
	google group: sci. optics

    Southern Microscope Service -  http://www.mindspring.com/~smskjc/ 

    The Microscope on a budget -
    http://www.mbstevens.com/mscope/index.html#top 

    Microscope - Depot   http://microscope-depot.com/contactus.asp 

    Light Microscopy Forum -  http://www.microimaging.ca/ 

    Nightingale  reconditioned microscopes -
    http://www.microscopesfromnightingale.com/ 

    " Insider Gemologist: - GIA What are Some Useful Microscope Lighting
    Techniques for Identifying Gemstones? " 

    You can learn more about the identification of gemstones in the GIA
    Gem Identification course. For information on GIA courses and diploma
    programs, click here, e-mail eduinfo AT gia.edu
    <mailto:eduinfo AT gia.edu>, or call 800-421-7250, ext. 4001. 

    A microscope offers many more lighting options than a loupe, and
    different types of lighting work best for seeing different gem
    features. The most useful techniques are fiber-optic darkfield,
    brightfield, diffused, surface-reflected, and polarized lighting. An
    overhead light source, as provided by a fiber-optic illuminator,
    makes it easier to see surface characteristics. Some microscopes
    come with a small fluorescent light or allow attachment of one to the
    stage for this purpose. You can also use a desk lamp, can be used
    with a loupe. For the general observation of surface characteristics,
    however, a fiber-optic system like the FiberLite works best. It also
    serves as a versatile supplementary light source that is vital for
    some separations, especially of synthetics and treatments. 

    Varying the lighting or using lighting combinations such as
    darkfield and fiber optics together can have a dramatic effect on the
    visibility and appearance of characteristics, and what can be
    determined by examining them. Surface characteristics visible in
    reflected light are usually invisible in darkfield light. And
    internal characteristics visible in darkfield light are often
    invisible in reflected light. Darkfield Illumination 

    Horizontal lighting created by a GIA Gem Instruments FiberLite
    reveals minute flux particles in a synthetic ruby. Most gemological
    microscopes have built-in darkfield illumination systems for
    examining inclusions. Turn on the microscope=92s internal light source
    and close the baffle in the light well so no light can enter the
    stone from directly below. Light enters the stone from the sides at
    an angle from behind, making some inclusions stand out brightly
    against a dark background. The degree to which a characteristic
    stands out against the surrounding gemstone is called its relief. For
    example, included crystals are minerals trapped within a gem as it
    grows. The brassy, metallic surfaces of included pyrite crystals
    stand out readily in pale emerald, so they are described as having
    high relief. An included crystal=92s relief depends on its refractive
    index (RI), its degree of transparency, and often its color,
    especially compared to the color of the host gem. A cluster of
    moderately sized, colorless calcite inclusions in a blue sapphire
    might be much harder to see than a few black chromite crystals
    scattered around the interior of a pale green peridot. Most included
    crystals are relatively easy to see with darkfield illumination.
    Other characteristics, like fluid liquid inclusions-pockets in gems
    filled with fluids and sometimes other materials-might require
    different lighting techniques because it is often difficult to see
    into their interiors using darkfield. Horizontal lighting is a
    fiber-optic illumination technique, where a narrow "pinpoint" beam of
    light is directed toward the side of the stone. Aim the light
    straight at the stone or from an oblique angle. Pinpoint crystals and
    gas bubbles stand out as bright objects when viewed from above. 

    Brightfield Illumination Brightfield illumination-sometimes called
    transmitted light-results from opening the light well=92s baffle so th=
e
    light is transmitted directly through the stone to your eye. To keep
    from being dazzled by the bright light, close the iris diaphragm so
    the opening is smaller than the stone. This will create shadowed
    transmitted illumination. If necessary, adjust the intensity of the
    light source with the rheostat. With the light well baffle open,
    brightfield illumination transmits light up through a transparent
    stone to your eye (left). Shadowed brightfield illumination is
    created by keeping the baffle open and closing the iris diaphragm
    until the opening is smaller than the stone. If not properly
    controlled, brightfield illumination may make many inclusions look
    dark and featureless against an overly bright background. If it is
    shadowed by closing the iris diaphragm, however, it works well for
    seeing low-relief features like curved striae in flame-fusion
    synthetics. Curved striae are structures that represent the layers of
    crystal growth around the cylindrical or rod-shaped boule, which is a
    typical product of the flame-fusion process. 

    Shadowed brightfield illumination reveals gas bubbles and curved
    striae in a flame-fusion synthetic ruby, while the gas bubbles are
    highlighted using pinpoint fiber-optic lighting. The brightfield
    technique works best if the light is shadowed by closing the iris
    diaphragm and restricting the light source to a small opening
    directly under the stone. This allows fine structures like curved
    striae to be seen more clearly. Shadowed brightfield illumination can
    be created by rocking and tilting the gem under darkfield lighting.
    This creates alternating dark and bright backgrounds that can be
    helpful for detecting flash-effect colors in fillers-seen principally
    in fracture-filled diamond and emerald-or determining if an inclusion
    is liquid, solid, or opaque. Rocking and tilting a treated emerald to
    alternate dark (left) and bright (right) backgrounds revealed an
    orangy yellow to blue flash effect in the filler. Diffused Lighting
    Diffused light can be created by opening the baffle and placing a
    tissue or a piece of translucent white plastic on the stage over the
    well (left). Diffused lighting reveals uneven color zoning and color
    zoning at facet junctions in this titanium diffusion-treated
    sapphire (right). Photos by Eric Welch.For diffused lighting, open
    the baffle and the iris diaphragm and cover the stage opening with a
    white, translucent material. Facial tissue or even the white plastic
    diffuser from the microscope=92s overhead light source can be used.
    Diffused light can help to observe the contents of liquid inclusions
    in natural gems. It is especially good for detecting curved color
    banding in flame-fusion synthetics. And it is excellent for detecting
    uneven color zoning in some lattice-diffusion-treated corundum, where
    the facet edges stand out against the white background. 

    Surface-Reflected Lighting Fiber optics, darkfield, brightfield, and
    diffused lighting make many inclusions easier to see, but
    surface-reflected light works better for blemishes and certain types
    of inclusions. To examine a gem=92s blemishes, position the light
    source, which is usually the microscope=92s overhead light unit
    (although fiber-optic illumination is actually more suited to this
    task and works much better), so the light reflects from the gem=92s
    surface. The light should strike the gem=92s surface at close to a 90=B0
    angle-this is called vertical overhead illumination. Thin, flat
    inclusions-like the thin films seen in many rubies-are also easiest
    to see when light reflects from their surfaces. But you cannot use
    vertical overhead illumination to see internal characteristics like
    these because reflections from the gem=92s surface block the view of
    the stone=92s interior. Instead, you need to use a light source-such a=
s
    a fiber-optic light-to direct a narrow beam of light at the stone
    from an oblique angle. Light entering the stone in this manner
    reflects from internal fractures, cleavages, and fingerprints, and
    makes them much easier to see without creating distracting surface
    reflections. 

    Polarized Lighting Polarized light can be created with a microscope
    by opening the baffle, placing one polarizing filter over the light
    well, and holding another between the stone and the objectives.
    Rotate the handheld polarizing filter to cross the filters. Polarized
    light can be created by opening the microscope=92s baffle and placing
    one polarizing filter over the light well and another between the
    stone and the objectives. Hold the second filter or attach it to the
    microscope just below the objectives. The microscope then functions
    as a magnifying polariscope. Use this type of lighting to distinguish
    doubly refractive included crystals from singly refractive solid
    inclusions or similar-looking gas bubbles or fluid-and/or gas-filled
    cavities. Crystals might show interference colors, and are often
    surrounded by halos caused by strain, while cavities or gas bubbles 
    won=92t have these features.


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