Diatomaceous earth for Class 11 is a soft, powdery rock made from the fossilized shells of microscopic algae called diatoms, and it is rich in silica. In your NCERT/NEET biology context, it is mainly remembered as a siliceous sediment formed by the accumulation of diatom shells on the sea bed over millions of years, forming thick deposits.

Quick Scoop: Class 11 Answer

  • Diatomaceous earth (also called kieselguhr) is a soft, porous, siliceous sedimentary rock.
  • It is formed from the fossilized, silica-rich cell walls (frustules) of diatoms that settle at the bottom of oceans and lakes.
  • In Class 11 Biological Classification, diatoms belong to the group Chrysophytes under Kingdom Protista, and their massive accumulation gives rise to diatomaceous earth.

Important properties (as expected at your level)

  • Light, porous and gritty powder due to its tiny, intricate silica skeletons.
  • Chemically mostly silicon dioxide (about 80–90% silica).
  • Very good at filtration because of its porosity.

Uses you should remember for exams

For Class 11 / NEET level, the most important use to remember:

  • Used as a filtering medium (for example in sugar, beverages, oils, and in laboratories) due to its high porosity.

Higher-level/extra uses (good for understanding, usually not all asked in exams):

  • Used as an insulator in furnaces and boilers because it is heat-resistant and porous.
  • Used as a mild abrasive (in some polishes and cleaners).
  • Used as a natural insecticide: its sharp particles damage the outer covering of insects, causing them to dry out.

One-line exam-style definition:
“Diatomaceous earth is a soft, siliceous sedimentary deposit formed by the fossilized shells of diatoms, used mainly as a filtering medium.”

Mini story to remember

Imagine an ancient ocean crowded with countless tiny glass-like boats (diatoms).
When each boat “dies,” its glass shell sinks to the bottom. Over millions of years, the sea floor becomes a thick, chalky “glass dust” carpet. Humans later dig this up, grind it, and use this powder as filters and insulators. That fossil glass dust is what you call diatomaceous earth.

SEO-style meta description (for your post):
Diatomaceous earth in Class 11 biology is a soft, siliceous sedimentary rock formed from fossilized diatoms, important for its porous nature and use as a filtering medium and insulator.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.