The chemical formula of Agate is indicated by SiO2 or Silicon Dioxide. Agate is actually a banded, multicolored, variety of Chalcedony. It is most commonly occurring in an infinite amount of color and patterns. It is also important to note that, no two Agates are alike. The extraordinary beauty and uniqueness of Agate is responsible for its great popularity. Agate, however, must be polished well to bring out its full charm and splendor. This is so because unpolished specimens are dull and ugly. It usually forms in rounded nodules or knobs which must be sliced open to bring out the internal pattern hidden in the stone. Agate is usually found leaving a white streak when rubbed on a white porcelain streak plate. The hardness measure of the mineral when it is evaluated using the Mohs scale method is usually 7. Agate is known to crystallize in the hexagonal system of crystal formation. In optical mineralogy, the hexagonal system of crystallization comprises crystals having four axes. Three of which are positioned in a single plane with equal length and are symmetrically spaced. The fourth axis is found to be perpendicular to the other three axes. It is however important to note that Agate, being a microscrystalline variety of quartz does not occur in crystals. It is commonly found occurring in botryoidal, mammilary, stalatitic, massive, nodular, as smooth rounded peebles, as banded, and in geodes. Most Agate crystals are found transparent to opaque in appearance. The specific gravity measure of Chalcedony is usually found ranging from 2.6 to 2.7 grams per cubic centimeters.

 

            Agate is usually found showing vitreous, waxy, or dull luster when viewed in reflected light of polarizing microscope used in the field of optical mineralogy. Some yellow or brown varieties however are found resinous. Agate has no cleavage found even when it is closely evaluated with the aid of petrographic polarizing microscope used in optical mineralogy. Agate is usually found showing conchoidal fracture when viewed under polarized microscopes. It also has brittle tenacity. Many Agate specimens found that fluoresce, usually green or white color that appears very interesting. Agate is also found showing tribolumininescent effect as well as piezoelectric.             There are actually hundreds of Agate types that were coined with special variety names. Most of them are actually hardly known, and new ones are made up every year. Most of the names however, have no scientific support.