diamond vs quartz

Diamond is the hardest known natural material and one of the two best known forms (or allotropes) of carbon, whose hardness and high dispersion of light make it useful for industrial applications and jewelry. (The other equally well known allotrope is graphite.) Diamonds are specifically renowned as a mineral with superlative physical qualities — they make excellent abrasives because they can be scratched only by other diamonds, Borazon, ultrahard fullerite, or aggregated diamond nanorods, which also means they hold a polish extremely well and retain luster. About 130 million carats (26,000 kg) are mined annually, with a total value of nearly USD $9 billion. About 100 tons are synthesized annually.[1]

圖片參考：http://upload.wikimedia.org/wikipedia/commons/2/22/Diamond_Cubic-F_lattice_animation.gif


Quartz is one of the most common minerals in the Earth's continental crust. It belongs to the hexagonal crystal system, and is made up of silicon, (SiO2), tetrahedra. Quartz has a hardness of 7 on the Mohs scale. Density is 2.65 g/cm³. The typical shape is a six-sided prism that ends in six-sided pyramids, although these are often twinned, distorted, or so massive that only part of the shape is apparent from a mined specimen. Additionally a bed is a common form, particularly for varieties such as amethyst, where the crystals grow up from a matrix and thus only one termination pyramid is present. A quartz geode consists of a hollow rock (usually with an approximately spherical shape) with a core lined with a bed of crystals.

diamond........... strong electrostatic force between them
quartz................weak van der waals force