Note: A white to colorless mineral composed of calcium oxalate monohydrate. Whewellite is formed on the surface of marble and limestone due to the presence of microorganisms, such as lichen. It also occurs in geodes, or septarian nodules; associated with coal measures and surrounding rocks with organic material, and in some uranium deposits. As microscopic crystals in living plant cells and as calculi or as a sediment in the human urinary tract. Named for William Whewell an English naturalist, scientist, and inventor of the system of crystallographic indexing.