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Some of my favourite rocks
Dec. 19th, 2013 10:27 pmGarnet schist comes first, of course - well, it has to, really: it's why I'm a geologist. Specifically, the garnet schist from the Rotmoosferner above Obergurgl, in the Oetztal in Tirol in Austria. A Google image search for Granatglimmerschiefer is indicative.
After that, I think it has to be serpentine, and particularly Lizard serpentine: it's what you get when you shove huge amounts of water through the mantle (about three times the rock volume, because you need to carry away the waste product from the chemical reaction too...). There's relatively few places where significant quantities are exposed at surface level - ophiolites are weird and rare things, and we're still not quite sure how they happen. Kynance Cove, Cornwall is my favourite exposure - it's six miles along the coast path from home, in at least one sense of home, and it's that stretch that I could pretty much walk with my eyes closed. (But it's a different stretch that has the amazing green-and-purple not-exactly-augengneiss outcropping down the sides of a headland atop which is an Iron-age fort, and I'm very fond of that, too.)
Blueschist is quite fun, for all it's metamorphic, in that it's actually blue. Along a similar theme, labradorite is gorgeous - and it's a feldspar, of the same class of mineral as plagioclase feldspar, which is always and forever my favourite mineral to look at under cross-polarised light, because PINSTRIPES.
I've got soft spots for every rock series I've ever worked on - the Borrowdale Volcanic Group; the Soufriere Hills Volcano; my current grab-bag of ocean island basalts - but at the end of the day what it probably comes down to for me, if I had to pick one only, is garnet-bearing granite. Because - granites are full of plag, and they're igneous, and you can do all sorts of fun science on them; and they're gorgeous; and, well, garnets. Garnets are, as I say, the reason I'm a geologist.
After that, I think it has to be serpentine, and particularly Lizard serpentine: it's what you get when you shove huge amounts of water through the mantle (about three times the rock volume, because you need to carry away the waste product from the chemical reaction too...). There's relatively few places where significant quantities are exposed at surface level - ophiolites are weird and rare things, and we're still not quite sure how they happen. Kynance Cove, Cornwall is my favourite exposure - it's six miles along the coast path from home, in at least one sense of home, and it's that stretch that I could pretty much walk with my eyes closed. (But it's a different stretch that has the amazing green-and-purple not-exactly-augengneiss outcropping down the sides of a headland atop which is an Iron-age fort, and I'm very fond of that, too.)
Blueschist is quite fun, for all it's metamorphic, in that it's actually blue. Along a similar theme, labradorite is gorgeous - and it's a feldspar, of the same class of mineral as plagioclase feldspar, which is always and forever my favourite mineral to look at under cross-polarised light, because PINSTRIPES.
I've got soft spots for every rock series I've ever worked on - the Borrowdale Volcanic Group; the Soufriere Hills Volcano; my current grab-bag of ocean island basalts - but at the end of the day what it probably comes down to for me, if I had to pick one only, is garnet-bearing granite. Because - granites are full of plag, and they're igneous, and you can do all sorts of fun science on them; and they're gorgeous; and, well, garnets. Garnets are, as I say, the reason I'm a geologist.
