Blackboard ‘chalk’ are produced especially for use with blackboards in white and also in various colours. White chalk sticks are made mainly from calcium carbonate derived from mineral chalk rock or limestone, while colored or pastel chalks are made from calcium sulfate in its dihydrate form, CaSO·2HO, derived from gypsum. Chalk sticks containing calcium carbonate typically contain 40–60% of CaCO (calcite). As compared to whiteboards, blackboards still have a variety of advantages: On the other hand, chalk produces dust, the amount depending on the quality of chalk used. Some people find this uncomfortable or may be allergic to it, and according
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,