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 Most people first encounter the word "chalk" in school where it refers to blackboard chalk, which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased.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
Pick-up sticks Pick-up sticks Pick-up sticks or pick-a-stick is a game of physical and mental skill in which a bundle of "sticks", between 8 and 20 centimeters long, are dropped as a loose bunch onto a table top, jumbling into a random pile. Each player in turn tries to remove a stick from the pile without disturbing any of the others. The game is known by several names including jackstraws (or jack straws), spellicans, and spillikins, and appears in a line of a nursery rhyme: "...five, six, pick-up sticks!" The sticks may be made of almost any material, such as ivory, bone,