
1) Horn silver
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https://www.crosswordclues.com/clue/cerargyrite

• (n.) Native silver chloride, a mineral of a white to pale yellow or gray color, darkening on exposure to the light. It may be cut by a knife, like lead or horn (hence called horn silver).
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http://thinkexist.com/dictionary/meaning/cerargyrite/

gray, very heavy halide mineral composed of silver chloride (AgCl); it is an ore of silver. It forms a complete solid-solution series with bromyrite, ...
Found on
http://www.britannica.com/eb/a-z/c/46
Ce·rar'gy·rite (se*rär'jȳ*rīt)
noun [ Greek
ke`ras horn +
'a`rgyros silver.]
(Min.) Native silver chloride, a mineral of a white to pale yellow or gray color, darkening on exposure to the light. It may be cut by a knife, like lead or horn (hence called
ho...Found on
http://www.encyclo.co.uk/webster/C/46

Cerargyrite is native silver chloride, a mineral of a white to pale yellow or grey colour, darkening on exposure to the light. It may be cut by a knife, like lead or horn (hence it is also called horn silver).
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http://www.probertencyclopaedia.com/browse/HC.HTM

Silver chloride
Found on
http://www.translationdirectory.com/glossaries/glossary075.htm

a very soft mineral, silver chloride, AgCl, used as an ore of silver; horn silver.
Found on
https://www.infoplease.com/dictionary/cerargyrite
No exact match found.