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 Most people first encounter the word "chalk" in school where it refers to blackboard chalk, which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased.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
Blackboard bold written as codice_2. The codice_3 package loads codice_1. In Unicode, a few of the more common blackboard bold characters (C, H, N, P, Q, R and Z) are encoded in the Basic Multilingual Plane (BMP) in the "Letterlike Symbols (2100–214F)" area, named DOUBLE-STRUCK CAPITAL C etc. The rest, however, are encoded outside the BMP, from codice_5 to codice_6 (uppercase, excluding those encoded in the BMP), codice_7 to codice_8 (lowercase) and codice_9 to codice_10 (digits). Being outside the BMP, these are relatively new and not widely supported. The following table shows all available Unicode blackboard bold characters. The symbols are nearly