Page 9 - Curriculum Visions Dynamic Book

Fluorite
Fluorite is calcium fluoride, a mineral that exists as beautiful cubic (box-shaped) crystals in greens, blues and yellows. It is a relatively soft mineral that can be scratched with a knife. It is commonly found in thick salt beds and also in veins and near hot springs. One of the most interesting properties
of fluorite is that it glows – fluoresces – in ultraviolet light.
chloride: a substance containing chlorine.
desertification: a process whereby a soil
is allowed to become degraded to a state in which crops can no longer grow, i.e. desert-like. Chemical desertification is usually the result of contamination with halides because of poor irrigation practices.
fluorescent: a substance that gives out visible light when struck by invisible waves such as ultraviolet rays.
halide: a salt of one of the halogens (fluorine, chlorine, bromine and iodine).
halite: the mineral made of sodium chloride.
osmosis: a process where molecules of a liquid solvent move through a membrane (filter) from a region of low concentration to a region of high concentration of solute.
playa: a dried-up lake bed that is covered with salt deposits. From the Spanish word for beach.
saline: a solution in which most of the dissolved matter is sodium chloride (common salt).
Iodine and bromine
Iodine and bromine do not make rock- forming minerals. Instead, they are usually all found in sea water. Some kinds of seaweed and molluscs are naturally rich in iodine and can be used as sources of the element.
 This seaweed is a natural scavenger of iodine from sea water. Coastal farming communities often use it as a natural fertiliser.
Halite
Common salt, or sodium chloride, forms thick beds. Sometimes it occurs as crystals. The crystals of the mineral, called halite or rock salt, are cubic (look closely at table salt to check this), glassy or white, but may also look pink because of iron staining. Halite is very soft and can be scratched by a copper coin.
Salt makes up four fifths of all the solids dissolved in the sea. Blood is also a salt (saline) solution in which red and white blood cells are suspended.
This is why, when people lose blood, doctors often administer a saline solution until a matching blood supply can be found.
The body uses the sodium ions for controlling osmosis and the chloride ions to control the nerves.
 Playa lakes are salt beds that form when temporary desert lakes dry up. The majority of these deposits are formed of sodium chloride, common salt that has been dissolved from rocks by rainfall and carried to lakes in the floods that follow torrential desert downpours. Playa lakes demonstrate the amount of salt that is carried in even “fresh” water.
9
9