X, A, 1 Smith, Edding field, Fanning : Philippine Minerals 85 



been found. It is frequently associated with primary and sec- 

 ondary manganese minerals, and is also frequently associated 

 with quartz in ore veins, there being a progression from quartz 

 to quartz-calcite, probably the result of lowering of temperature 

 and pressure. Calcite occurs also as a secondary mineral in ig- 

 neous rocks; also, as stalactites, stalagmites, and travertine. 

 Marble is found in Romblon and crystallized limestone at Mon- 

 talban. The mineral is used to manufacture quicklime for sugar 

 refining. Marble is used for monuments and building purposes. 



Chalcedony— SiO^+HgO. 



Chalcedony occurs in irregular milky white patches in jaspers 

 and other rocks in various parts of the Islands. 



Chalcocite — C U2 S . 



Chalcocite is a massive gray mineral usually secondary in the 

 upper zones. It is found in Misamis, Mindanao, and Mountain 

 Province, Luzon. There is no production in the Philippines. 



Chalcopyrite — CuFeSg. 



Chalcopyrite is the most universally distributed ore of copper. 

 It is found as small crystals in a large number of quartz veins, 

 and is associated mainly with galena and usually crystallizes after 

 galena. It is found in small quantities in all of the mining 

 districts. No commercial deposits are known in the Philippines. 



Chert— SiOj. 



Chert occurs as nodules in various formations in many parts 

 of the Archipelago, also as radiolarian cherts, probably of Juras- 

 sic age. It is well developed in Palawan, Panay, Ilocos Norte, 

 and Balabac, and is probably equivalent to the radiolarian "horn- 

 fels" of central Borneo. It has no economic use. 



Chlorite — HgMgg AlgSigO 1 «. 



Chlorite occurs as fine, green fibrous masses as an alteration 

 product in many igneous rocks. It has no economic use. 



Chromite — FeOCraOg. 



Chromite occurs associated with serpentine in heavy granular 

 masses with mottled black and green appearance in Antique Prov- 

 ince, Panay. There is some prospecting but no production. 



Chrysoprase — SiOz (colored by nickel oxide) . 



Chrysoprase occurs as beautiful leek-green pebbles in a river 

 near Butuan, Mindanao. One specimen, No. 180, is in the col- 

 lection of the Ateneo de Manila. This mineral could be used 

 as a gem. 



