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).
In the USA sand is usually classified by grain size into five main categories: very fine (1/16 â 1/8 mm), fine (1/8 â 1/4 mm), medium (1/4 â 1/2 mm), coarse (1/2 â 1 mm) and very coarse (1 â 2 mm).urther classification of sands is based on the consideration whether the sand has resulted from processes related with animal and plants life (biogenic sands) or resulted from rocks transformations (mineral sands).