The silicates tossup had multiple fine answers available for a while. Mike already mentioned "mafic minerals," which was the most tempting option I could think of for a while--it would be weird/silly to start off a tossup on mafic minerals by saying that they contain iron and magnesium, but that clue certainly points more to mafic than to silicates in general. Other silly possible answers off early clues include "silicates whose crystal structure consists of isolated tetrahedra" (as opposed to single-chain or framework or all the other silicate structures). There are certainly different levels of specificity of mineral classifications ("these minerals are all based on Si04 tetrahedra" or more specifically "these minerals are all based on rings of Si04 tetrahedra").Captain Scipio wrote:See, this is what people mean when they say that the question reflects poor understanding of how minerals are classified. I'll bet you that I can come up with no fewer than 10 "groupings" that contain olivines (or even both olivines and feldspars.) You, Andy Watkins, seem to be under the impression that minerals are classified in only one way; this is wrong in the extreme.everyday847 wrote:...The smallest (and largest) grouping containing olivine is silicates. Feldspars don't have any magnesium and iron, so they're just wrong, but even so, the smallest grouping that contains them is the subclass "tectosilicates," and after that, silicates...
It's true that feldspars aren't orthosilicates, but there is a major subtype of feldspar known as orthoclase. There are multiple clues before "an ortho- one" that rule out feldspars, but "an ortho- one" doesn't feel like a great way to rule out feldspars on its own.everyday847 wrote:So I've discovered all the points where people may have negged. For reference:
5) I've said olivine explicitly now. Also, I don't think there are ortho- micas or feldspars. (These are the two most common negs, survey says.)I wrote:15. One of this kind of mineral,(1) whose crystals also contain magnesium and iron, (2) is at the top of Bowen's reaction series, (3) while zircon contains this mineral class's characteristic group and zirconium. (4) In addition to olivine, an ortho- one, (5) one variety of a group of these was the source of the first rubidium to be discovered, (6) while another is best known for its perfect basal cleavage and the thin sheet into which is breaks: (7) those varieties are known as lepidolite and muscovite. Their best known subclass is the tecto-ones, all of which contain aluminum save the best known group of them. Examples of the alumino-ones include zeolites and feldspars. For 10 points, identify this class of minerals, like quartz and mica, all of which include oxygen and silicon.
Anyway, I pretty much agree with Mike's assessment--this question was a strange mix of very clear clues seemingly pointing in several different directions interspersed with some opaque clues: as I heard the question go by, "top of Bowen's reaction series" seemed like a rather easy clue to 2 possible answers (or groups containing those answers), olivine was a similarly easy clue but by then I was just confused about what kind of answer you were going for, then there's a juicy clue for micas but the answer can't be micas, etc. In the meantime, there's stuff on "the source of the first rubidium to be discovered," which a quick trip over to Wikipedia leads me to believe is a reference to lepidolite. I'm not really sure why an indirect reference to lepidolite comes after "olivine"--the latter sure seems more well-known to me.
p.s. I think I wrote the only other earth science tossup of the tournament (sea-floor spreading). It's not my favorite tossup I've ever written by a long shot, but if anyone feels like it was particularly bad I'd be interested in hearing about it (here or by email: [email protected]). I also wrote the tossup on metric/metrics; if anyone has a complaint more specific than "I don't like math tossups on terms" I'd also be interested in hearing about that.