I had good ol’ Dave Young for Intro, Structural, Mineralogy, and Optical Min. Oh, and he was a co-instructor for Oceanography. He’s a hell of a prof- the backbone of my small alma mater’s even smaller geology dept. He’s planning on retiring soon, I’m sure to the dismay of the rest of the faculty. For those of you who have trouble convincing your Christian friends about the realities of geologic time, his Christianity and the Age of the Earth gives a good explanantion.
Aw, shucks… I’d better not start on trace elements–gotta save something for later! (Once I get started on high field strengths, I don’t let up…)
You know, I actually met Dave Young a week ago last Sunday. He and I both attended a field trip to southern Mass. and Rhode Island to look at Devonian-Permian granites and their Nb-Y-F pegmatites. (I bought the book a couple of days later, and it took another couple of days to make the connection…) Not only was he a nice guy, but we saw amphiboles and magnetites that were SUPER-HUGEMONGOUS!
Which reminds me of a story (hey, we get few enough geology threads, I’m by God gonna hijack this one)…John Brady from Smith and Jack Cheney from Amherst do joint Pet field trips, and on our trip to the Adirondacks, we went to Gore Mountain to see the famous garnets, which were billed by Jack as “Garnets as big as your head!” I pointed out that, given the size of Jack’s head, those were large garnets indeed. Hey, I was in John’s class, I could insult the guy. And he does have a really big head.
Well, I hope we don’t PO mannyet al, but apparently geochat trudges on. Along the lines of Pantellerite’s post, I was well into this career before I realized that my high school and college buddy’s dad who was throwin’ me out of their house at 3:00 AM was the (Swami Niijinandu) geodoggie who came up with Dunham’s Matrix System of Mineral Classification.
Well, according to our dear John Brady, cited in this paper, written by a Smith student: “They are composed of approximately 37 - 43 percent pyrope, 40 - 49 percent almandine, 13 - 16 percent grossular and 1 percent spessartine (Brady, 1996).” So the answer is yes, except for uvarovite. Those garnets really are fabulous, if you’ve never seen them; they are indeed huge, and have a parting that makes them very valuable as industrial garnets rather than gems. The garnet amphibolite is really distinctive; I can pick it out at 50 paces. In fact, I love running across it because it makes me sound so knowledgeable. “What do we have here? Some Gore Mountain garnet? Why, so it is!”
Ditto what Geobabe said–I’m just killing time waiting for a follow-up on the OP. What minerals did he finally chose and what did he say about them? (And I’ll echo another of her comments: Geology posts are precious few and we need to milk them for all they are worth!)
Sounds like I’m going to have to find those garnets someday. The only garnets 'round here are in a minor garnet-biotite schist in the Van Horn Mountains. Almandine, I think, and industrial grade at best. Still cool, though… What’s more, my lecture today includes a discussion on garnets!
Ringo, that’s awesome that the Swami Baghwan Dunham kicked you out of the house. I know that Folk is still kicking and mostly active, but what we’ve all wanted to know is: is Dunham still alive? Or has the Baghwan “called him home”?
Eh, I don’t think he’s coming back. He presumably has his paper written and handed in by now, with whatever help we were able to give him. And how could he be expected to know that there’s a whole thread full of anal retentive rockhoppers waiting with bated breath to hear how his paper came out?
And I was gonna come in here and say, “Hey, you two, get a room!” because I don’t get many chances to say that, but then I got sucked into the discussion.
My “oh, come on!” alarm went off. Cite?
[sub]not for whether Jack said that, silly–for whether they really are as big as your head
Somebody else go Google it, I’m drinking coffee[/sub]
Actually, the link Geobabe provided does cite that the garnets are up to 1 m in diameter (mind you, most are not, but some are roughly head-sized). And here’s another link–brought to us by Google; scroll down to the listing for New York:
That’s too bad, I don’t care too much for them carbonate rocks, but I always did like Dunham’s classification better than Folk’s. Something about saying “Wackestone” or “Wacke-Packstone”, I guess. I am surprised that you saw him in the '80s, only because I’d been lead to believe that he’d moved to Oregon and had never been seen again!
[looking at Darby the Prof standing in front of her rock wall]
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Words fail me.
Soooo…we’re talking about something that’s basically absolutely worthless, right? I mean, these things are, first of all, embedded in solid rock, and second, even if you could chip them out, what would you do with them? You can’t sell them, they’re no good as jewelry, huh?
So we’re talking novelty value alone? Of interest only to geologists?
And here all this time I thought garnets were those itty-bitty dark red stones in antique rings. I mean, MAN, those are some BIG…ASS garnets, ya know?
Well, Duckie, they are both cool to look at, and, market value notwithstanding, they allow some observations about what was going on at the time. That’s their true (academic) value.
I think my main pursuit, which is perhaps shared with my geologist friends (remember, I am not a geologist, but I count many amongst my friends ), is not so much focussed on the value of a particular specimen as it is on this piece’s place in unraveling the story of what paleoenvironment went on to create the environment we now find.
In other news, Pant, the illustrious (and he was) Dr. D may have wandered off into the woods - the last time I saw him was in Austin for his son’s wedding - he was considerably less orange than in his heyday. I think Folk ultimately outflanked him in setting a standard.
Duck, those particular garnets are not gem quality. The main reason they are not is not that they are embedded in rock–it’s not really that hard to cut off a hunk of rock and whittle away the bits you don’t want. The Gore Mountain garnets possess a quality called parting–which is not the same as cleavage, more on that in a moment–that makes them very valuable as industrial garnets, abrasives mostly.
Cleavage, if you are not familiar with the term, means the tendency of a mineral to break along specific planes, due to the crystalline structure. Some minerals can be distinguished by a distinctive cleavage (so can some geologists, but we’ll leave that for MPSIMS). Garnets do not have a cleavage and usually break with a conchoidal fracture, like glass does, which leaves a surface that looks a bit like a conch shell, hence the name.
The parting of the Gore Mountain garnets means that unlike the typical garnet fracture, they break into wedges or slivers, and tend to continue breaking into slivers, continually creating fresh cutting surfaces, which is why they are such good abrasives. The Barton Mines Company mines and markets these garnets.
Thanks for the inside scoop on Dunham, Ringo. Interesting guy–and not nearly as “shallow” as Folk. And you’re a Geo-something, and that’s all that matters… even if that “-something” is “-physicist”. (But I guess there aren’t any rocks in Houston, anyway–what are you going to do?)
DDG, I am floored by your assumption that any rock or mineral is “useless”! First, like Ringo mentioned, there is the great academic value of these garnets, which undoubtedly preserve a great deal of the metamorphic (and thus tectonic) history of that area. Second, like Geobabe mentioned, there’s hardly anything that doesn’t have an important industrial mineral application. (I’m glad to see that this has steered towards industrial minerals, which are an occasional part-time pursuit of mine!) Those garnets may make lousy semi-precious gems, but I’ll betcha they’d make a great sandpaper…
“Useless” minerals, indeed!
(p.s., nice discussion on mineral cleavage v. parting there, Geobabe!)