A raphide crystal occurs in plant cells, and its main function is to repel animals away from plants. The crystals are shaped like needles, and are formed from calcium oxalate.
Raphides and raphide crystals are found in more than 200 different species of plants. Raphides have a sharp end, and when consumed, release a toxin that is harmful to a plant's predator. Stinging and burning can occur in the mouth of a predator who has eaten a raphide crystal, and esophageal damage can occur. A lethal dose of raphide crystal to an animal like a field mouse is 15 mg/kg.