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felsic & mafic
Dec. 31st, 2024 07:07 amfelsic (FEL-sik) - adj., of igneous rocks, containing primarily light-colored minerals such as feldspar, quartz, and other silicates with relatively high concentrations of aluminum, sodium, and potassium.
mafic (MAF-ik) - adj., of igneous rocks, containing dark-colored minerals with relatively high concentrations of magnesium and iron.
The terms can be used technically in the lab with reference to their chemical makeup or loosely in the field to describe rock colors. Both types contain silicates, so silicon isn't mentioned. Mafic was coined in a 1912 paper by a team of American geologists from ma(gnesium) + f(erric), containing iron + -ic. Felsic was coined around the same time from fel(dspar) + -ic, but I haven't been able to confirm whether this was done by the same team. More research needed obsv.
Administrivia: skipping tomorrow for the holiday -- have a safe and happy Gregorian New Year, everyone!
---L.
mafic (MAF-ik) - adj., of igneous rocks, containing dark-colored minerals with relatively high concentrations of magnesium and iron.
The terms can be used technically in the lab with reference to their chemical makeup or loosely in the field to describe rock colors. Both types contain silicates, so silicon isn't mentioned. Mafic was coined in a 1912 paper by a team of American geologists from ma(gnesium) + f(erric), containing iron + -ic. Felsic was coined around the same time from fel(dspar) + -ic, but I haven't been able to confirm whether this was done by the same team. More research needed obsv.
Administrivia: skipping tomorrow for the holiday -- have a safe and happy Gregorian New Year, everyone!
---L.
