Chelsea (Jadeite) Filter for testing COLORED Gemstones

What does it do?

This filter allows transmission of both deep red wavelengths around 690 nm and yellow-green wavelengths, around 570 nm, that match emerald’s emission and absorption characteristics, it was initially recommended to assist the discrimination between natural emerald and its simulants such as green glass, tourmaline, peridot etc. This discrimination was possible because chromium -- containing iron -- and vanadium free emeralds emitted a red fluorescence when illuminated by white light that had a content of ultraviolet wavelengths.

Synthetic emeralds were commercially introduced around 1940. These produced the same pink-red response as some emeralds through the Chelsea filter. However, although this filter was unable to predictable discriminate between natural and synthetic emerald, it was subsequently found capable of distinguishing aquamarine, blue topaz and their blue synthetic spinel simulants, for unlike natural gemstones blue cobalt-containing synthetic spinels emitted a red fluorescence under white light.

HOW TO USE A CHELSEA FILTER

Hold the filter an inch or two from the eye. Light the stone with a strong light bulb or torch. The stone may appear to change colour. The filter must be held near to the eye but there is no need to hold the filter close to the stone, even items in showcases can be examined providing they are lit by strong lights.

Warranty:  Every unit comes with a 1 Year Warranty against defects!