Gemstone Windows and Dark Patches: What to Look for in a Cut Gem

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AI-generated educational illustration. Conceptual only; not a photograph of an actual specimen or location. A coloured gem may have a pale, see-through centre or areas that look almost black. Both affect its appearance, but they do not have the same cause. What is a window? A window is an area where light passes through the gem instead of being returned towards the viewer. You may see the background through it, especially near the centre. Cutting angles and the material's refractive index—how it bends light—help determine whether this happens. There is no single ideal depth for every gemstone. Why dark patches need a closer look Darkness can have several causes. The material may absorb a lot of light. Some facets may reflect dark surroundings or the observer. Extinction is another cause, involving light that is not returned to the viewer after internal reflection. For that reason, calling every black patch “extinction” can be misleading. A simple viewing routine Look at the gem fac...
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Requirement for a well-equipped gemological laboratory for analysing gemstones/diamonds

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Establishment of   well equipped Gemological laboratory  For Gemstones / Diamond  Testing Certification

1.     Natural Gemstones samples e.g Emerald, ruby, sapphire (Cut/rough)

2.     Treated gemstones samples (dyeing, filling, heat treated etc)

3.     Composite stones (double/triplet)

4.     Synthetic gemstones samples (made by all manufacturing process such as flux, flame fusion etc.)

5.     Natural diamonds

6.     Treated diamonds (HPHT, glass or wax filling , irradiated etc)

7.     Synthetic diamonds

8.     Diamond Imitation stones (CZ, GGG) etc

9.     Master stones of diamonds (For diamond color Grading)

10.                        Energy dispersive x-ray fluoresces (EDXRF), Positive identification of rage gem material, separation of jade group, turquoise and diamond from its simulants in  parcels, separation of natural from synthetic gems, origin determinations , identification cabochons and mounted stones.

11.                        The Raman Spectroscopy, gemstones and material identification, identification of inclusions exposed at the surface and within gem materials, separation of natural from synthetic material, separation of amorphous and poly crystalline/ microcrystalline materials.

12.                        X-Radiography, photographs of the internal structure of pearls and other materials

13.                         FTIR (Fourier Transmissions Infrared Spectroscopy)

14.                        Gemological Microscope 45x but extendable to 120 x.

15.                        Immersion Microscope with attached Polaris filters.

16.                        Refractometer analog (sample) with liquid

17.                        Refractometer Digital

18.                        Ultra Violet Lamp with Short waves/long waves

19.                        Spectroscope

20.                        Specific gravity Balance

21.                        Specific gravity liquids

22.                        Polariscope

23.                        Dichroscope

24.                        Chelsea filter

25.                         Loupe 10x

26.                        Tweezers (sample, lock, prong)

Location: Peshawar, Khyber Pakhtunkhwa, Pakistan

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