Diatoms are also called as 'Pearls of Ocean',why? What is diatomaceous earth?

(N/A) Diatoms are called 'Pearls of Ocean' because they are the primary producers in the ocean,forming the base of the aquatic food chain,and their cell walls are impregnated with silica,which gives them a glass-like,shimmering appearance under light.
Diatomaceous earth is the accumulation of the cell walls of diatoms over billions of years. Since these cell walls are made of silica and are indestructible,they form large deposits on the ocean floor. This soil is gritty,chemically inert,and used in polishing,filtration of oils and syrups,and as an insulating material.