Is pumice mafic?
ANDESITE Andesite is an extrusive volcanic rock with a composition that is intermediate between basalt and rhyolite….Classification of Igneous Rocks.
| TEXTURE | Vesicular |
|---|---|
| Felsic | Pumice |
| Intermediate | Scoria |
| Mafic | Scoria |
What is the color index of igneous rocks?
The color index of an igneous rock is a measure of the ratio of dark colored, or mafic, minerals to light colored, or felsic, minerals. Speaking broadly, mineral colour points out the specific gravity of the mineral, as minerals that are lighter in color tend to weigh less.
What is the mafic color index of basalt?
between 50 and 90
Rocks with colour indices between 50 and 90 are termed ‘mafic’ rocks (e.g. basalts).
What is the name of an igneous rock that has a color index of 65?
Minor amounts of dark-colored (mafic) minerals like amphibole and biotite mica may be present as well. Felsic igneous rocks are rich in silica (in the 65-75% range, meaning the rock would be 65-75% weight percent SiO2) and poor in iron and magnesium. Intermediate is a composition between felsic and mafic.
Is pumice mafic or felsic?
felsic
Scoria and Pumice Scoria is a mafic volcanic glass. It is an extremely vesicular basaltic lava with very small (< 1mm) vesicles. Pumice is a felsic volcanic glass.
What texture is pumice?
Vesicular
Pumice
| Type | Igneous Rock |
|---|---|
| Texture | Vesicular |
| Origin | Extrusive/Volcanic |
| Chemical Composition | Felsic |
| Color | White |
What is the colour index?
colour index, in astronomy, the difference between two measurements of the magnitude (brightness on a logarithmic scale) of a star made at different wavelengths, the value found at the longer wavelength being subtracted from that found at the shorter.
Which type of rock has lighter color?
The most general classification is based on the relative abundance in a rock of felsic (feldspar and silica-quartz) minerals vs mafic (magnesium and ferrum or iron) minerals. Felsic minerals (quartz, K feldspar, etc) are light colored while mafic minerals (hornblende, pyroxenes) are normally dark colored.
What is the color index of obsidian?
| Obsidian | |
|---|---|
| Category | Volcanic glass |
| Identification | |
| Color | Deep black or blackish green |
| Fracture | Conchoidal |
Is pumice intrusive or extrusive?
extrusive volcanic rock
Pumice is a type of extrusive volcanic rock, produced when lava with a very high content of water and gases is discharged from a volcano.
What is pumice composition?
The chemical properties of pumice will vary from deposit to deposit, but essentially, pumice is primarily Silicon Dioxide (Amorphous Aluminum Silicate), some Aluminum Oxide, and trace amounts of other oxides.
What is the luster of pumice?
silky luster
Pumice usually has a silky luster whereas pumicite is more earthy (Williamson and Burgin, 1960). Pumice and pumicite are usually light colored, commonly light gray to white, but shades of light buff, brown, and pink are common.