Some of my favourite rocks
Dec. 19th, 2013 10:27 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
kaberettGarnet 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.
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Date: 2013-12-20 12:10 am (UTC)This reminds me though - this quotation (from our bookclub book this month, but Googled for pasting):
2007, Robert MacFarlane, The Wild Places, Granta Books (2009), ISBN 9781847081599, unnumbered page:
On a rock ledge, I found and kept a heart-sized stone of blue basalt, beautifully marked with white fossils: coccoliths no bigger than a fingernail, the fine fanwork of their bodies still visible.
Plausible? Basalt forming by flowing over these things somehow? Fossils in an igneous rock raised my eyebrows...
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Date: 2013-12-20 01:37 am (UTC)(no subject)
Date: 2013-12-20 10:06 am (UTC)(no subject)
Date: 2013-12-20 03:02 am (UTC)Separately: in my case garnets have been A Thing That Is Special ever since a rather-small-me found, in the "assorted shiny rocks" section of a toystore, a rock with garnets sticking out of it (approximate reaction: "I can have a rock with jewels in it this is the coolest thing ever"). So I am pleased to see your why-garnets-are-special, because a)stories, and b)that one rock.
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Date: 2013-12-20 03:07 am (UTC)OOH OOH IS IT TIME FOR THE ETYMOLOGY OF POMEGRANATE IS IT IS IT IS IT
THIS IS MY FAVOURITE GAME
OKAY SO. French for "pomegranate" is "grenade". Yes, like the explosive weaponry. This is on account of if you drop them when they're ripe, they burst, scattering seeds everywhere. (Well, that's why grenades are that way round, at any rate.) Meanwhile the English is from the Latin via the Old French, apple of many seeds; BUT IT GETS BETTER BECAUSE, you see, the German for pomegranate is Granatapfel, garnet-apple.
...
MY FAVOURITE GAME.
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Date: 2013-12-20 03:19 am (UTC)(no subject)
Date: 2013-12-20 09:32 pm (UTC)(no subject)
Date: 2013-12-21 12:43 am (UTC)(no subject)
Date: 2013-12-22 08:34 am (UTC)I'd not seen blueschist before. That really is quite something! (Hmm... maybe I should poke Dad to find out if they have any at his work). I am also quite a fan of labradorite. And there is always something a little hypnotic about garnets.
You've mentioned before that your mum also loves rocks. Has that always been the case?
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Date: 2013-12-22 11:26 pm (UTC)My favorite is actually man-made; synthetic cat's eye, which I'm blanking on the actual scientific name for. I love it; black is my favorite.
Otherwise, garnet, onyx, and obsidian are my others. I can't say I'm as much into the scientific side, but coming from a somewhat New Agey family, the healing properties associated with stones is something that I was very much into. Even if there is no scientific backing for this, I feel comforted by them, and I figure anything that makes me feel better is worthwhile. :)