2.1 - IN GREATER DEPTH
WATER AND ICE - MOLECULES AND CRYSTALS - Water is abundant on earth and life would be impossible without it. Water is an unusual substance. The molecule is asymmetrical and polarized. Thus, water is the universal solvent because other substances are attracted to water. Molecules are more tightly packed in liquid water than in ice, which forms hexagonal crystals by sharing hydrogen atoms and floats even though it is the solid phase. The fact that ice floats makes the climate of the earth habitable. If ice sank, bodies of water would eventually freeze solid. Water also expands when it freezes, which promotes mechanical weathering.

2.2 - IN GREATER DEPTH
BONDING - The attraction between ions involves a balancing of electromagnetic charges, and orderly internal arrangement of atoms characterizes all crystalline substances. Four types of bonding are recognized: 1) ionic, with fixed atom positions and transferred electrons, is typical of halite and is the most common in minerals; 2) covalent, with adjacent atoms sharing electrons, is typical of diamond; 3) metallic, characterized by free movement of electrons between atoms, is not important in geology; and 4) van der Waal's forces, residual charges, form the weak bonds that keep adjacent sheets of micas and graphite together.

2.3- ENVIRONMENTAL GEOLOGY
ASBESTOS-HOW HAZARDOUS? - Studies suggest that the treat from exposure to chrysotile or white asbestos, as opposed to blue and brown amphibolite asbestos, is overstated. The greatest threat seems to have been to asbestos workers who didn't wear protective clothing or those who smoked, and nonoccupational exposure risk is less than being struck by lightning. One estimate of the cancer death risk from asbestos is 1:100,000 (less than the risk of being struck by lightning). White asbestos fibers dissolve in lung tissue over a year, while fibers of blue and brown asbestos and fiberglass, now replacing asbestos, would not dissolve in a person's lifetime. Removal of white asbestos (about 95% of domestic use) from public buildings is unnecessary. Fiberglass is increasingly used as a substitute for asbestos!

2.4 - ENVIRONMENTAL GEOLOGY
CLAY MINERALS THAT SWELL - Clay minerals are sheet silicates with a variety of uses. Kaolinite is used as a food additive, particularly to thicken fast-food "milk" shakes. Montmorillonite adsorbs water between its silicate layers. This characteristic causes expansion and can cause problems for building foundations, although it may be useful in sealing cracks in bedrock or concrete.

2.5 - IN GREATER DEPTH
UNIT CELLS AND CRYSTAL SYSTEMS - Crystals are formed by the three-dimensional repetition of unit cells that are simple, closed geometric forms of identical chemical composition. Unit cells occur in only six basic shapes and those shapes determine the crystal system to which a mineral belongs. The shape of a unit cell can be determined from a mineral's symmetry either by visual examination of perfect crystals, or by X rays.

2.6 - IN GREATER DEPTH
ON TIME WITH QUARTZ - Piezoelectricity is a property of quartz in which pressure, either tension or compression, applied to a crystal creates an electric current. Electron flow reverses as pressure changes from tension to compression and back. In a reverse of the procedure, applying an electric current to a crystal causes it to expand and compress rapidly and regularly. These vibrations in quartz occur at the rate of about 100,000 per second with a variation of no more than one in 10 billion. Thus, precision quartz clocks lose or gain no more than one second in 10.