Chalk
Transcript: Former underground chalk quarry in Meudon, France Raw Materials Reuse and Recycling "Chalk and Limestone." Science Online. Facts On File, Inc. Web. 29 Oct. 2013. <http://www.fofweb.com/activelink2.asp?ItemID=WE40&SID=5&iPin=SVR0155&SingleRecord=True>. Sheridan, Rob. "Sidewalk Chalk and the Calcium Cycle." Earth Science Picture of The Day 19 Oct. 2009: 1. EPOD. Web. 29 Oct. 2013. <http://epod.usra.edu/blog/2009/10/sidewalk-chalk-and-the-calcium-cycle.html>. recycling process information Sheridan, Rob. Sidewalk Chalk and the Calcium Cycle. 19 Oct. 2009. EPOD. Web. 29 Oct. 2013. <http://epod.usra.edu/blog/2009/10/ sidewalk-chalk-and-the-calcium-cycle.html>. sidewalk chalk picture Secrest, Rose. "Chalk." Made How: 1. Print. most of chalk information "Chalk." Wikipedia 28 Oct. 2013: 1. Rpt. in 1. N.p.: n.p., n.d. N. pag. Wikipedia. Web. 29 Oct. 2013. <http://en.wikipedia.org/wiki/ Chalk>. previous uses information "Chalk." Wikipedia 28 Oct. 2013: 1. Rpt. in 1. N.p.: n.p., n.d. N. pag. Wikipedia. Web. 29 Oct. 2013. <http://en.wikipedia.org/wiki/ Chalk>. previous uses information "Chalk." Wikipedia 28 Oct. 2013: 1. Rpt. in 1. N.p.: n.p., n.d. N. pag. Wikipedia. Web. 29 Oct. 2013. <http://en.wikipedia.org/wiki/ Chalk>. previous uses information When you draw with chalk on the sidewalks it will eventually be washed away by rain and go through the local sewers, and end up back in the ocean. When it returns to the ocean it will continue the calcium cycle, and contribute to the dissolved marine calcium. Then, the marine salts will contribute to the other marine shells or remain undissolved which will, either way, create a new limestone or gypsum bed millions of years from now. Use of Chalk Chalk Chalk didn't become a standard in a classrooms until the nineteenth century. Chalk used to be used in agriculture to raise pH levels in soils with high acidity. Antacid properties make chalk ideal for polishing and cleaning. Toothpaste, for example, contains small amounts of chalk. Chalk is also used in fingerprint powder. Manufacturing Chalk Citations Calcium Carbonate is the main component in chalk. Calcium Carbonate is a form of limestone, which is formed when plankton skeletons decompose and turn into coccoliths, then the coccoliths accumulate and form sedimentary layers. The base component in pastel chalks is Calcium Sulfate, which is derived from a mineral evaporate of ocean brine called Gypsum. Pastel chalks also contain clays and oils for pigment. Quarry the limestone - The land over the limestone deposit must be removed with bulldozers and scrapers, then holes are drilled into the rock and explosives are placed inside to blow the rock apart. Pulverize the chalk - The limestone has to be transported to the crushing machine to pulverize the limestone to meet the chalk industry's standards (has to be primary crushed and secondary crushed). Then the chalk has to be wet ground to wash away the impurities. Rotating steel drums with steel balls inside pulverize the chalk until it's very fine and easy to write with. After the chalk is ground, it's sifted over vibrating screens to make even smaller, finer particles. The particles are mixed with water, shaped and cut to the proper length. The chalk is then placed into an oven, baked to at 188 degrees Fahrenheit for four days and cut to 80 millimeter lengths.