Gemstone Refractometers

Reliable classification and quality control of gemstones

Krüss offers two refractometer models, designated ER601 and ER604, for the classification and quality control of gemstones.

Krüss gemstone refractometers are offered either as a compact professional or standard version. They both provide a sharp image and good readability, and have the option to select LED illumination or ambient light with a sodium filter. They offer a measuring range of either 1.33-1.83 nD or 1.33-1.81 nD depending upon model selected, and have optical glass prisms, with accuracy to 0.01 nD and a resolution of 0.01 nD. This equipment is lightweight (at 0.4kg), and has an automatic multi-voltage power supply (110-220V).

All Krüss gem refractometer models are constructed of cast aluminium, and are supplied complete with a polarisation filter and manual.

For prices and availability information on Gem Refractometers, please contact your nearest Krüss distributor, who will be delighted to help.

Krüss Gemmo-Shop
You can find our Gemstone Refractometers in the Gemmo-Shop.


Classification and quality control of gemstones

To classify and quality control gemstones, a refractometer is normally employed. The equipment measures the Refractive Index (RI) and Birefringence, by passing light through the stone, which refracts out at a defined and consistent angle.

The RI is an important parameter in classifying a mineral or gemstone. Each mineral has its typical refractive index, due to its chemical composition; this is easily measured with a refractometer. (Gem structure can be crystalline or non-crystalline, and may have a single or multiple of microscopic crystals or amorphous mass). Gemstones with a high RI are generally more brilliant, ie a diamond has a RI of around 2.4, whereas quartz approximately 1.55 – this means that light travels in air at a velocity 2.4 and 1.55 times its velocity, respectively. The optical characteristics are derived from chemical composition and structure.

Most stones with flat or curved polished surfaces can be assessed using a gemstone refractometer.

Classification and quality appraisal techniques are important when so many synthetic gems are common, and cost a fraction of natural stones.

Gem refractometers are consistent and accurate, and are the professional’s instrument of choice.

ER604 gemstone refractometer
ER604 gemstone refractometer

ER601 gemstone refractometer
ER601 gemstone refractometer