X. A, 1 Smith, Eddinfield, Fanning: Philippine Minerals 91 



Muscovite— K2O.3AI2O3.2H2O. 



Muscovite occurs rarely in igneous rocks. It occurs more com- 

 monly in schists, particularly in a quartz muscovite schist in 

 Ambos Camarines. There are no economic deposits of this min- 

 eral in the Philippines. 



Niter— KNO3. 



Niter is said to be collected from certain caves on a small 

 island near Surigao, Mindanao, and is used by natives for making 

 gunpowder. This laboratorj^ has no definite information re- 

 garding this substance in the Philippines, and its occurrence 

 is to be doubted because of the heavy rainfall here. 



Oligoclase — (See Plagioclase) . 



Olivine— (Mg, Fe)2SiO,. 



Olivine occurs in many rocks in the Islands, particularly in 

 small greenish yellow grains in basalt and in so-called picrites 

 of Panay. It is of no economic value. 



Opal— SiOjHoO. 



Opal is found in small fragments, and occasionally in large 

 pieces of jasper. It occurs in Ilocos Norte and various other 

 localities, but is not of any commercial value as found in the 

 Philippines. One pretty specimen showing "fire" is in the 

 museum of Santo Tomas University. 



Orthoclase— K20.AL03.6Si02. 



Orthoclase occurs sparingly in some igneous rocks. It is of 

 no economic use. 



Osminm — Os (metallic). 



Osmium occurs with gold, iridium, and traces of platinum in 

 thin metallic plates in decomposed rock. The locality where the 

 mineral is found is said to be Luzon. 



Petroleum — Complex series of hydrocarbons. 



Petroleum occurs as a very light, paraffin-base oil in shales 

 in various parts of the Islands, notably in Bondoc Peninsula, 

 Tayabas, Luzon, and in Cebu. Two wells, one shallow and one 

 deep, have yielded a small amount of oil. 



PhiUppsite— (K„ Ca) ALSi,Oi2+4iH20. 



Philippsite occurs in characteristic white, radiating or tuffed 

 masses in Masbate. No economic use is made of it. 



Pickeringite (magnesia alum)— MgSO^.Al, (SO,) 3+22H2O. 



Pickeringite is found in long fibrous masses as efflorescence 



