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
The Chalk Garden " 'The Chalk Garden' is extraordinarily modern for a high comedy set in the drawing room of a stuffy Sussex manor house: its plot and structure are elliptical; its witty lines aren't brittle but are instead redolent with what the author calls 'the shape and shadow of life.'... Bagnold's play is in part a journey to the bottom of Miss Madrigal's identity; it is also about the effect the woman has on her employer's household. Mrs. St. Maugham is a selfish, eccentric paragon of privilege who spends her days gardening but can't make anything grow." The Chalk Garden The Chalk