रेफाइड
thumb|Raphides in Epipremnum ''Devil's ivy (600× magnification) Raphides ( ; singular raphide or raphis'') are needle-shaped crystals of calcium oxalate monohydrate (prismatic monoclinic crystals) or calcium carbonate as aragonite (dipyramidal orthorhombic crystals), found in more than 200 families of plants. Both ends appear needle-like, but raphides tend to be blunt at one end and sharp at the other.