Blackboard chalk is a writing instrument used for writing and drawing primarily on blackboards but can be used on other surfaces too. Blackboard chalk is made in a shape of a stick that is 10mm thick and 80mm long, out of calcium sulfate in its dehydrate form - as gypsum, or calcium carbonate.
First chalk (the natural one) was used in prehistory for cave drawings. Later, artists used chalk for sketching and some of these drawings survive until today because they were protected in shellac (a resin secreted by the female lac bug (Kerria lacca)).
The first chalk in sticks appeared when artists found them convenient. They made it by grinding the natural chalk (calcium carbonate), mixing it with water, clay and pigment (natural pigments were used like carbon for black or rust for red). Mix was then formed in sticks and dried. Blackboard chalk became popular in 19th century when classrooms became larger with more students and there was a question how to teach such a number at the same time. Chalks were used on large blackboards where teachers wrote to the whole class but also on small ones that were used by students at their desks. These boards were used for practice and had a small sponge for clearing the board. Blackboard chalk for use in classrooms was at first only white because the blackboards were... well, black (because they were made from slate) and white gave good contrast to the black.
Later, in the 20th century, classroom boards were made of synthetic materials. Although some thought that classroom boards should be yellow and chalk blue or purple to simulate written text, manufacturers started making classroom boards in green because that color does not train the eyes. As a good contrast teachers started using yellow chalk. Chalk is still manufactured in many different colors which helps with drawing of diagrams and in geometry.
Whiteboard pen (or a dry-erase marker) is a non-permanent marker that uses an erasable ink. Its main purpose is to be used on slick, non-porous writing surfaces like whiteboards and overhead projectors and to be easily erased without leaving marks with a dry eraser.
Before there were dry-erase markers there were wet-erase markers. These could not be erased by a dry eraser but with a wet cloth. After them came whiteboard pens. The first whiteboard pen was invented by Jerry Woolf who worked in Techform Laboratories. Later it was patented by Pilot Pen in 1975. Sanford made their dry marker called EXPO in 1976. It was a bulky marker and available in black, red, blue, and green. Later, Sanford added thin variants, less unpleasant odor and many more colors. Europe accepted whiteboard and dry markers in 1980s. United States had to wait until ‘90s.
Whiteboards appeared before dry markers - somewhere in ‘50s or ‘60s but we don’t know precisely when. One story says that a whiteboard was invented by Martin Heit, a photographer and Korean War veteran while the other gives this honor to Albert Stallion who worked at American steel producer Alliance. First whiteboards appeared on the market in 1960’s and were wet wiped. Then came dry marker and whiteboards started replacing blackboards because of allergies concerns and other potential health risks posed by chalk dust that was product of erasing blackboards. First whiteboards were made of enameled steel. Later were made cheaper variants of laminated chipboard, high pressure laminates and steel boards with a white synthetic (polyester or acrylic) coating. These have a characteristic to leave residue of erased markings on. Those of highest quality are made of enamel and are called porcelain or even glass boards.