Identifying Feldspar In Granite

Whereas quartz is an important mineral in the granite it s lacking in syenite.

Identifying feldspar in granite.

This lighter color is mixed with grains of other darker minerals creating the salt and pepper look. Feldspar is often the most abundant rock in a granite this is why the rock looks white with dark spots and not dark with white spots. Cases like that are helpful for learning to tell the feldspars apart. The differences can be subtle and confusing.

Visible crystals of pink feldspar white or grey quartz and black mica. Granite but is distinguished in the hand specimen by the absence of visible quartz. The polished granite actually a quartz syenite of a park bench displays large grains of the alkali feldspar mineral microcline. Look at the fracture pattern.

Generally it has a salt and pepper appearance about black and white. Check the color of the rock you suspect is granite. Feldspar quartz mica hornblend equivalent to. Alkali feldspar also called potassium feldspar or k feldspar has a color range from white to brick red and it s typically opaque.

Color is determined by mineral content. Many rocks have both feldspars like granite. Granite is formed by magma that cools very slowly into hard rock below or within the earth s crust. Careful examination will show that syenite is composed of long prisms of the dark mineral hornblende rather than the scaly biotite mica and feldspar which is the chief component of the rock.

Granite is made mainly of quartz feldspar biotite and muscovite. More below alkali feldspar has the general formula k na alsi 3 o 8 but varies in crystal structure depending on the temperature it crystallized at. There are two main types of feldspar. There is no horizontal banding in.

Applying this definition requires the mineral identification and quantification abilities of a competent geologist. It sometimes also contains hornblende augite magnetite or zircon. Granite always consists of quartz and feldspar which usually give granite a light almost glittery color ranging from almost translucent white from the quartz to a pale pink from the feldspar. Today prudent geologists identify potassium feldspars other than sanidine simply as alkali or in some cases potassium feldspars when describing rocks on the basis of macroscopic examination.