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 Most people first encounter the word "chalk" in school where it refers to blackboard chalk, which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased.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
Austin Chalk Austin Chalk The Austin Chalk is an upper Cretaceous geologic formation in the Gulf Coast region of the United States. It is named after type section outcrops near Austin, Texas. The formation is made up of chalk and marl. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus. The Austin Chalk consists of recrystallized, fossiliferous, interbedded chalks and marls. Exposures of Austin Chalk are mainly seen in quarries, roadcuts, and stream beds where the water eroded the soil. The Austin Chalk outcrops and can be seen