Iâve come across a historical footnote on the English language and I thought everyone would get a kick out of it. Up until about 2 hundred years ago, there was a 27th letter in the English language. This letter is still in common use today and I would bet that you have used it recently. But this letter is no longer considered a letter; it is now regarded either an abbreviation or punctuation. Iâm talking about the (&) ampersand.
Gneiss is a medium to coarse-grained, irregularly banded rock with only poorly developed cleavage. The light and dark bands (gneissic banding) are alternations of felsic vs. mafic layers. Slate is a product of low grade metamorphism (not terribly great burial temperatures and pressures are required).
Sorting (sediment) Sediment consisting of well sorted grains (left) compared with poorly sorted grains (right). Sorting describes the distribution of grain size of sediments, either in unconsolidated deposits or in sedimentary rocks. This should not be confused with crystallite size, which refers to the individual size of a crystal in a solid. Crystallite is the building block of a grain. Very poorly sorted indicates that the sediment sizes are mixed (large variance); whereas well sorted indicates that the sediment sizes are similar (low variance).