NEW YORK MINERAL LOCALITIES 



Gabbros, diorites and other basic igneous rocks. Rocks of this 

 series have for their chief feldspar constituents the plagioclases ; 

 both orthorhombic and monoclinic pyroxenes occur as com- 

 ponent minerals. The formation of individual crystals takes 

 place as the rock grades from finer to coarser structure and gives 

 rise to strings or zones of crystallized minerals rather than 

 pockets and cavities as is the case with granite. 



COMMON MINERALS FOUND IN BASIC IGNEOUS ROCKS 



magnetite labradorite garnet 



ilmenite enstatite biotite 



spinel hypersthene chrysolite 



albite pyroxene titanite 



anorthite 



Metamorphic rocks 



Gneisses. Typical gneiss differs but little in mineralogic com- 

 position from typical granite. The mineral constituents are, 

 however, to be found in larger and better formed individuals 

 along zones of contact with crystalline limestone and local areas 

 of magmatic segregation. 



COMMON MINERALS FOUND IN GNEISS 



graphite hematite sillimanite 



chal copy rite orthoclase cyanite 



pyrite albite allanite 



marcasite amphibole tourmalin 



quartz pyroxene staurolite 



corundum garnet muscovite 



spinel vesuvianite biotite 



magnetite zircon monazite 



rutile andalusite apatite 



Crystalline limestones. The crystalline limestones are prolific in 

 accessory minerals which occur disseminated through the mass 

 of the rock, in pockets or vugs or in zones of contact between the 

 limestone and an adjacent igneous intrusive rock. 



