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3D3DCat's whisker detector.
This appears to be a modern reproduction of an antique cat's whisker detector used in crystal radio sets. The dark sparkly crystal is galena (lead sulfide), and the copper wire touching it is the "whisker". If the wire touches the crystal just right the junction operates as a diode, allowing electricity to flow in one direction only. This allows the device to convert an amplitude-modulated radio signal into an audio signal you can hear.
Source: eBay seller jrschades
Contributor: Theodore Gray
Acquired: 28 March, 2009
Text Updated: 29 March, 2009
Price: $24
Size: 3"
Purity: 86%