Chelsea Filters | Gemstone Identification Tools

Chelsea Filter

Also known as the emerald filter or beryloscope, the Chelsea filter is an auxiliary tool used in gemstone identification. It consists of highly selective color filters designed to absorb specific wavelengths of light while allowing only red and some yellow-green light to pass through. By blocking all other visible light, this specialized optical filter enhances certain color properties, making it easier to differentiate gemstones based on their composition and color reactions.

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Technical Specifications

Filter material: Optical glass filter with color selectivity
Durability: Fade-resistant and securely bonded, ensuring long-term use
Casing: Sandblasted aluminum alloy for a refined and durable finish
Observation method: Requires a strong light source; light should be transmitted through or reflected off the gemstone. The filter must be held close to the eye, with the gemstone positioned approximately 25cm away
Dimensions: 55 × 35 × 10mm
Filter Diameter: 25mm
Net Weight: 30g
Packaging: Comes with a protective leather case

Application

The chelsea filter is a useful tool for distinguishing certain gemstones and their synthetic counterparts based on selective light absorption. It is suitable for:

Identifying natural emeralds and imitations. Most natural emeralds appear green under the filter, while synthetic emeralds typically turn red.
Distinguishing natural and treated jadeite. Natural green jadeite remains unchanged under the filter, whereas dyed jadeite appears red.
Differentiating natural and synthetic spinel. Natural blue spinel does not change color, while cobalt-colored synthetic spinel appears red.