• Webster's Revised Unabridged Dictionary
    • n Proustite (Min) A sulphide of arsenic and silver of a beautiful cochineal-red color, occurring in rhombohedral crystals, and also massive; ruby silver.
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Century Dictionary and Cyclopedia
    • n proustite A native sulphid of arsenic and silver, occurring in rhombohedral and scalenohedral crystals and also massive. It has a beautiful cochineal-red color, and is hence called ruby silver, or light-red silver ore; the latter name is given to distinguish it from the other form of ruby silver, pyrargyrite, which is dark-red or neatly black, and is called dark-red silver ore. Magnificent specimens of proustite are obtained from the mines of Chanarcillo in Chili.
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Webster's Revised Unabridged Dictionary
From the French chemist, J. L. Proust,


In science:

Due to commercial unavailability of quality cuts of some the strong candidates, such as gallium selenide (GaSe) and proustite (Ag3AsS3 ), we obtained instead a custom cut of silver thiogallate (AgGaS2 ) and a commercially mass-produced periodically poled lithium niobate (PPLN, sold as Thorlabs OPO-3).
Single barium ion spectroscopy: light shifts, hyperfine structure, and progress on an optical frequency standard and atomic parity violation