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submitted 5 months ago by fossilesque@mander.xyz to c/science_memes@mander.xyz

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[-] MossyFeathers@pawb.social 35 points 5 months ago* (last edited 5 months ago)

Fuck off. You can't just say things like that without telling the class what the difference is.

Edit: it looks like the right one has white specks and the left one doesn't? Can't tell if the white specks are actually there or just image compression or different lighting though.

[-] fossilesque@mander.xyz 48 points 5 months ago

You are right, my bad. :) One is granite and the other one is granodiorite.

Granite is a rock with certain minerals in certain ratios: quartz, alkali feldspar(AF) and plagioclase(PL), where there is more AF than PL.(+accessory minerals of course but let's keep it simple). Granodiorite has more PL than AF. For more information, look up the Streckeisen diagram, it's a little scary at first but there are good explanations of it. :)

Sauce: https://www.reddit.com/r/Geologymemes/comments/1cqg1yb/how_identifying_rocks_feels_like_sometimes/