Chalcedony (Silicate-Framework)
Si02Hardness: 7.0
Specific Gravity: 2.65
Characteristics: Fibrous microcrystalline varitey of quartz; vitreous luster; conchoidal fracture; only soluble in HF.
A common mineral found in igneous rocks, many metamorphic rocks, and most sedimentary rocks.
Chalcedony is primarily used as a decorative stone in collections and some jewelry.
(Primary text: Perkins, D. 2002. Mineralogy. Prentice Hall.)