Visual Encyclopedia

Chalk

Chalk ( /ˈɔːk/) is a soft, white, porous, sedimentary carbonate rock, a form of limestone composed of the mineral calcite. Calcite is an ionic salt called calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite shells (coccoliths) shed from micro-organisms called coccolithophores. Flint (a type of chert) is very common as bands parallel to the bedding or as nodules embedded in chalk. It is probably derived from sponge spicules or other siliceous organisms as water is expelled upwards during compaction. Flint is often deposited around larger fossils such as Echinoidea which may be silicified (i.e. replaced molecule by molecule by flint).

The description above is licensed from Wikipedia under the Creative Commons license.

Add an image or video to this topic

No signin required

or

Processing...

Cancel

Best posts about this topic

Loading . . .

Ad

not just normal chalk, HAIR CHALK!

Contributed by Rachael Alexandra

What is Sussle?

Sussle is the first, open visual encyclopedia. Anyone can use it.

What's a visual encylopedia?

It has beautiful images and viral videos that are way more fun than reading all the text in traditional encyclopedias.

5 reasons you should add your own images and videos:

  1. If you found Sussle interesting, then give back by adding something interesting for others.
  2. Help others learn in a fun way.
  3. Make someone else interested in this topic laugh or say wow!
  4. Become internet-famous as people like and share your post.
  5. It's super easy, so it won't take more than a minute.

Ready to start?

Just click on the red module above.