Jewelry Appraisal and Repair Houston

Gemological Instruments

FURTHER TESTING

OTHER GEMOLOGICAL TESTING INSTRUMENTS

Though the microscope is our best friend. The instruments listed below provide us with additional testing procedures that can confirm a gemstone's identity.

These instruments are essential provided they are used correctly by the Gemologist. It takes experience to become an expert.

The Jeweler's Loupe

It is used to assign a diamond's Clarity grade. The loupe is a valuable resource for identifying gemstones in the field.

To use a Jeweler's Loupe, raise the loupe and position it an inch from your eye. Then lift the object to be viewed; bringing it slowly toward the loupe until you see a crisp magnified image. The item should come into view approximately one to two inches from the loupe.

The Refractometer

If the microscope were a tank, the refractometer would be a canon. The Refractometer is a vital asset of every Gemologist's arsenal.

Every gemstone refracts light uniquely. This device measures the bending of light rays as they strike and pass through the gemstone.

It's readings are very precise and it is second to the microscope. The Refractometer is one of the most reliable and trusted pieces of gemological equipment.

$The Refractometer$

The Polariscope

By using polarized filters, this instrument identifies whether or not a stone is singly refractive, doubly refractive, or an aggregate.

A doubly refractive gemstone splits light rays as they enters the stone, where as a singly refractive gem does not. Hence, the single and double prefixes. This is another important characteristic to identifying a gem.

The Carat Scale

Because 1 Point (0.01ct) of a Carat can greatly define the value of a diamond.

For Example

A 1.00ct diamond is in a much greater pricing category than a 0.99ct (90pts "points") diamond. The rise in price from 0.99ct - 1,00ct is significant.

It is imperative the scale is accurate. The scale should have a highly sensitive, quality balance that is precise.

UV Raman Spectroscopy

The vast majority of natural diamonds, comprised mostly of Carbon atoms, have Nitrogen related defects that can be excited by ultraviolet radiation and measured. It distinguishes both, HPHT and CVD laboratory-grown diamonds; as well as imitations.

This device (GIA iD100®) combines advanced spectroscopic technology with years of diamond and gemstone identification research.

The Spectroscope

Each Gemstone has its own pattern of light absorption on the Visible Color Spectrum. This is wavelengths measuring 380 to 750 nanometers on the Electromagnetic Spectrum.

These patterns become detectable as light passes through the stone and is recorded by the scope.

The Dichroscope

The Dichroscope isolates colors within dichroic and pleochroic gems. Here we can see the separation of colors in a Blue Sapphire. You can identify a violetish Blue color in the top square image and a slightly greenish Blue color at its bottom. Some gemstones exhibit three colors, such as Tanzanite. This is known as Pleochroism.

Specific Gravity

Testing for Specific Gravity (relative density) measures the ratio of a gemstone's mass in air as it corresponds to water.

Even Ruby's relative density is just slightly higher than that of Blue Sapphire. You would not mix the two up, but considering they are from the same gem species (which makes them very close to eachother), they still measure differently.

This can be a great confirmation test when extra information is necessary.

Long-Wave | Short-Wave Fluorescence

Short-wave (SWUV; 254nm) and long-wave ultraviolet (LWUV;365nm) radiation can assist in distinguishing natural gemstones from lab grown gems. The process can also determine if a gemstone has been assembled; put together. Flame-Fusion Synthetic Blue Spinel emits red fluorescence when exposed to LWUV and a chalky blue fluorescence under SWUV . Diamonds, natural Rubies, and many other gems fluoresce. A gem can also phosphoresce; continue to fluoresce after exposure of radiation has been terminated. Fluorescence cannot identify a stone, though it is added confirmation.

Immersion Cell & Diffuser Plate

Immersion Cells filled with methylene iodide and a diffused light source can reveal cement joints for assembled stones, curved growth structure in Synthetic Colored Gemstones, and it can undercover Lattice Diffusion; where a gem is blasted with foreign elements to improve color.

Submerging a stone in Methylene Iodide can provide you with various evidence.

Gemstone Color Filter

A color filter can expose treatments, as well as lab grown or synthetic gems.

Here is a deeply colored Citrine gemstone. Vivid Citrine Quartz is rare; most of them in the market are heat treated from Amethyst Quartz.

As you can see, there is a reaction due to the heat treatment of this gem. The color of the gemstone is Orange, though it appears purple under the filter.