Color is a spectacular and variable property of minerals. Some minerals always have the same color and their name often denotes the color. Azurite is derived from the Persian word for "blue," Lazulite from the Arabic word for "heaven" and Pyrope from the Greek word for "fiery-eyed."
In other cases color is not at all an intrinsic property of the mineral. Beryl, celestite and fluorite all occur in a variety of colors.
Color centers, or F centers, are a common cause of colors, especially in the group called "alkali halides." Electrons occupy the sites which normally would have been occupied by anions (negative ions). These electrons are described as F centers and their absorption of visible radiation causes the coloration of the mineral.Free electrons may be produced by radiation and on long exposure to natural radiation, calcite, fluorite, halite and other minerals show coloration produced in this way.
Gypsum is that soft stuff that can be scratched with a fingernail, glassy luster, hardness only 2+, gravity 2.3, with a fluorescence in yellow, often showing an hourglass pattern within the crystal. It is colorless, or of light tints, sometimes banded or sometimes evenly colored. Plaster of Paris is made from it because it is only calcium sulfate loosely combined with water. The gypsum is heated and part of the water of crystallization is driven off. When water is again added the plaster of Paris is changed back to gypsum. This very widespread mineral is a fine species to collect because of the great variety of inexpensive specimens available.
Meteorites are very scarce, so few are found. But once a meteorite is found, the question of ownership comes up. If the object is recovered on land belonging to an individual, ownership belongs to the holder of the deed to the land, and not the finder. In the case of the great Williamette meteorite litigation over the ownership was finally settled by the Oregon State Supreme Court who rendered their decision in these words: (Lange 1962) "Meteorites embedded in the earth are real estate and consequently belong to the owner of the land in which they are found."On the other hand if a meteorite is found on land owned or controlled by the United States government, under the Act of Congress, June 8, 1906, it may not be removed unless allowed by the US government through the Smithsonian Institution, whose permission must be obtained before a meteorite may be moved if lying on federally controlled land (Linsley 1939). Reference: Mineral Information Service, July 1966, "The Meteorites of California" C.P. Butler.