Intracellular deposits of which element is known as plant opals

Intracellular deposits of Silicon element is known as Plant opals.
Plant opals are microscopic amorphous siliceous bodies that occur in living plants. It can also be called a plant-derived silica body excavated from the soil.
These are commonly found in plants in the leaf epidermis and outermost covering of seeds and fruits, the epidermis of bracts that surround and protect grass seeds and in the sub-epidermal tissue of orchid and palm leaves.