raphide
noun
raph·ide ˈra-ˌfīd 
plural raphides ˈra-ˌfīdz
ˈra-fə-ˌdēz
: any of the needle-shaped crystals usually of calcium oxalate that develop as metabolic by-products in plant cells
Example Sentences
Recent Examples on the Web These contain crystals of calcium carbonate called raphides, which take the form of microscopic needles. 
Kenneth Setzer, miamiherald, 14 June 2018
Kenneth Setzer, miamiherald, 14 June 2018 Word History
Etymology
French & New Latin; French raphide, from New Latin raphides, plural, from Greek rhaphides, plural of rhaphid-, rhaphis needle, from rhaptein
First Known Use
circa 1842, in the meaning defined above