Chalk It is formed in the sea by sub-microscopic plankton, which fall to the sea floor and are then consolidated and compressed during diagenesis into chalk rock. Most people first encounter the word "chalk" in school where it refers to blackboard chalk, which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased. Blackboard chalk manufacture now may utilize mineral chalk, other mineral sources of calcium carbonate, or the mineral gypsum (calcium sulfate). While gypsum-based blackboard chalk is the lowest cost to
Chalk outline fairy" is occasionally used to describe an officer that makes the chalk outline, often without authorization and while unwittingly contaminating the scene. While the use of chalk is uncommon, investigators may make smaller marks, or use removable flags, index cards, or even markers, to indicate important positions, particularly if other references are not available. Chalk outlines of bodies are familiar tropes in popular culture. Often they are used in humorous ways depicting awkward positioning or meticulous precision, or portending a character's impending death by having them prematurely fall into a drawn outline. "The Naked Gun" series made extensive use of