Chalcedony

Synonyms: stone myeloid 
Chemical composition: SiO2 
Characteristics: Aphanitic, the proportion of 2.58 ~ 2.64, due to low water content than the quartz. Under the microscope in Radiology fibrous, have waxy luster, transparent to translucent, or transparent when particle size has a different ribbon structure. White chalcedony matrix porosity between grain or crystal face, such as incorporation of impurities that is affected by a different color. The same general composition and quartz, although for caustic potash erosion, can be the difference between quartz. 
Occurrence: the quality produced in the andesite agglomerate, the department increased by hydrothermal irregular invasive in the filling. Coastal Range of chalcedony, mainly by volcanic activity in the region rose to shallow hydrothermal when its temperature and pressure drops, so that the role of silica generated leaching, transformed into the chalcedony Aphanitic; also provided through the non-uniform crystallization the course of, or intrusion into irregular folds or fissures. 
Uses: Gemstone (semi-precious stones), decorations and ornamental crafts.