Ooid Is A Type Of Sand That Grows
Sand is a term for worn down fragments of any material. Gravel has a diameter bigger than 2mm, and silt is smaller than 0.063mm; anything in between is sand. Ooid, however, is the only sand that accretes rather than erodes. It accumulates calcium in the ocean until it is a grain the size of a pin tip.
from Deep Look
Key Facts In This Video
Sand can be any material that has been worn down until it's reduced to tiny fragments. (0:17)
Silt is just sand that is finer than 0.063mm (0.0025in) in diameter. (0:27)
Ooid is the only sand that accretes rather than erodes. (1:40)