Australian Facetors' Guild Limited

Cutting Notes from the Dop

  • 15 Dec 2016 9:30 AM
    Message # 4460486
    Anonymous member (Administrator)

    New Sapphire treatments:

    "NEW GEMSTONE TREATMENTS". As the gemstone treatment saga continues the following "new" products are now available in the market: 
    1. Lead-treated orange, yellow, yellow-greenish sapphires. Starting material is previously rejected light yellowish, light pinkish, light yellow-greenish natural sapphires treated with the lead-filling process using Pb-based additives. The treatment is unstable.

    2. Surface Cobalt Diffusion Treated natural sapphire. Starting material is near-colorless natural sapphire treated with the surface diffusion process using Co-based additives. Color penetration to 0.3-0.4 mm below the surface. The treatment is unstable

    3. Surface Cobalt Diffusion Treated flame-fusion sapphire. Starting material is colorless flame-fusion sapphire treated with the surface diffusion process using Co-based additives. Color penetration to 0.3 mm below the surface. The treatment is unstable
    The word "gem" is relative and loosely used; it should be redefined. Fluxed-treated gemstones with/without chromophores and fillers are actually semi-synthetic, hybrid, or composite products and do not qualify to be called “GEMS”. Only untreated gems should be called “GEMS”. –Dr. Franken-Stone, Grandmaster of Gem Treatments 

    Have your say 
               

    Last modified: 20 Sep 2017 10:10 AM | Anonymous member (Administrator)
  • 15 Dec 2016 9:33 AM
    Reply # 4460489 on 4460486
    Anonymous member (Administrator)

    Peridot 
    Colour: Various shades of green. Apple green to Emerald green is the best quality colors also can be very pale yellow green, to olive green. 
        
    Mohs’ Scale Hardness: 6.5 to 7 
    Specific Gravity:         3.27-3.37 
    Cleavage:                  Imperfect 
    Refractive Index: 1.65 -1.69 
    Critical Angle:   37.31-36.78 
    Double Refraction: +0036 
    Dispersion: 0.020 

    Notes: 
    Peridot generally cuts easily. It is the polishing that usually causes the cutter problems. 
    I always choose a deep design with a higher number of facets. 
    Peridot can be stunning in bigger sized stones. If you can get them. 

    I have been told to try the following: Is to mix straight white vinegar with A02on a tin lap. The acid of the vinegar seems to really promote a good polish on the facets. 

    Warning if you use this method then make sure you clean your machine 
    Vinegar is a very mild acid. It is not good for your faceting machine. 

    Cutting Notes: 
    Orientate for the best color and yield. Peridot tends to be included with  carbon spots and lily type pads are very common. 
    Peridot is a difficult material to check for clarity so really take your time when picking your rough look for the best clean material. 
    Peridot works well in almost any design; I prefer deeper designs with brilliant facets. 

    Polishing: 
    I Pre polish with 3000 Diamond on copper lap.  Changing your polishing 
    direction is sometimes helpful because, Peridot tends to have differing  hardness  and  direction. 
    Commonly polished on lead tin alloy lap,  ceramic lap, copper, or composite lap such  as  a last lap, with 14,000, 50,000, 100,000 diamond. 

    Happy Cutting 
    The Dop 

    Last modified: 15 Dec 2016 9:49 AM | Anonymous member (Administrator)
    Merged topic from AFG Forum: 15 Dec 2016 9:45 AM
  • 15 Dec 2016 9:47 AM
    Reply # 4460495 on 4460486
    Anonymous member (Administrator)

    TOPAZ 
    Color:  Colorless, Very Light Blue, Green, Yellow, Red-brown and light to dark blue usually radiated in labs 
    Mohs’ Hardness:   8 
    Specific Gravity:   3.53 3.56 
    Cleavage:  Perfect, Perpendicular to  "c” axis 
    Refractive Index: 1.610 1.638
    Critical Angle:        37. 84  - 38.40 
    Double Refraction: +0.008+0.010 
    Dispersion: 0.014  (low) 
    Heat Sensitive:        No 

    Notes 
    I do not recommend Topaz for a beginner because it can occasionally be very difficult to polish.  Some Topaz just seems to be easier to work with than others. It is common for some colours of topaz to fade in ultra violet light.   
    If you are in doubt of the stability of colour in some Topaz rough, leave the rough exposed to direct sunlight for a few weeks. If it is going to fade it will, do this before you cut it. 

    Cutting Notes: 
    Orientation for best color, is important,  "c” axis is usually the best color. 
    Because of perfect cleavage, Topaz must be oriented at least 7 degrees off of  "c" axis. Direction does not matter as long as the table and any major facets are not on the C axis Cleavage. Avoid excessive pressure, and knocks. Random, cleavage direction can promote abrading of facet edges. Generally this happens during the final polishing stages and can cause a lot of problems, to a new facetor. 

    Polishing: 
    What I use: 3000 Diamond on copper or 8,000 and 50,000 diamond on Zinc laps. 
    Commonly polished on lead\tin alloy lap using aluminum oxide. Ceramic lap, or composite lap, such as a last lap, with 14,000, 50,000, 100,000 diamond. 
    Or what ever works best for you 

    The Dop 

    Last modified: 15 Dec 2016 9:50 AM | Anonymous member (Administrator)
    Merged topic from AFG Forum: 15 Dec 2016 9:48 AM
  • 15 Dec 2016 9:54 AM
    Reply # 4460497 on 4460486
    Anonymous member (Administrator)

    To start: The good old Sapphire. 

    SAPPHIRE 
    Colour: Blue in various hues, colorless, pink, red (Ruby) purple, orange, yellow, green and the Parti coloured, including color change in various shades 

    Mohs' Hardness: 9 
    Specific Gravity: 3.99-4.00 
    Cleavage: none 
    Refractive Index: 1.766-1.774 
    Critical Angle: 34.40 34.50 
    Double Refraction: 0.OO8 
    Dispersion: 0.018 (med) 
    Heat Sensitive: No 

    Notes* 
    Good Sapphire rough is difficult to get. 
    Man-made Sapphire generally cuts easily with no problems. But natural Sapphire can sometimes be very difficult to orientate and work with. 
    For lightly saturated material Try cutting them for Quartz angles generally have work for me. 
    I have found Pitting on some facets is common; Do as  JB states = I have found that the pitting or "orange peel" is not a problem if the pre-polish is deep enough.  In my experience it will not come out with the final polish.  Best to get rid of it at the pre-polish stage.  I change direction on the lap and this often does the trick 
    Cutting Notes: 

    Orientate for the best colour. Be sure to inspect Sapphire rough in different lighting conditions because it tends to change color depending on the light. 

    Hardness differs in different directions and heated stones can often be more directional because of the heating. 

    Assume all Sapphires are heated unless you know for sure they are natural. 
    Sapphires are usually heated to improve colors and get rid of silk. 

    Pre polish 3,000 on copper lap, 8,000 and 50,000 Diamond polish on Zinc laps. 
    Commonly polished on lead\tin alloy lap, copper, ceramic lap, or composite lap (such as a last lap), with 14,000, 50,000, 100,000 diamond or whatever works best for you. 

    The Dop

    Last modified: 15 Dec 2016 9:55 AM | Anonymous member (Administrator)
    Merged topic from AFG Forum: 15 Dec 2016 9:54 AM

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