My Iceland class ended today except for grading, which hopefully I’ll have done by the end of tonight. We have a week free (research!) and then the spring semester starts. I have two classes this spring: mineralogy and structural geology. I’ve taught both before 2 or more times, so I have a basic outline of what I want to cover & how, but am tweaking things here and there.
One aspect I added to mineralogy on the last round was adding the concept of “mineral of the week” and reading a paper from Geology about that mineral. I can’t claim credit for the idea of a mineral per week — I picked it up at the Using Visualizations SERC workshop (uh, my picture is on the front page…) from Darby Dyar who was talking about her new textbook. My copy of her book is at work, but ch. 1 includes the “big 10 minerals.”
The following September, Chuck at Lounge of the Lab Lemming posted a top 50 list of minerals. Several people commented, but the meme took a turn when Callan asked for top 5 minerals that students should know.
Callan went with:
- quartz
- plagioclase
- clays
- olivine (maybe garnet, spinel & perovskite?)
- ice
- quartz
- calcite
- pyrite
- clays
- olivine
- quartz
- calcite
- clays
- iron oxides
- olivine
- quartz
- calcite & aragonite
- olivine
- smectite
- apatite
Ok, why am I dragging this up again? I have 13 weeks to fill to assign minerals to this spring and I only have 12 minerals. I’m looking for opinions about what my 13th mineral should be–or even arguments about why I should drop one and swap in two other minerals!
My current list:
- quartz
- K-feldspar
- plagioclase
- muscovite
- biotite
- amphiboles (yes, I grouped them)
- garnet
- olivine
- pyroxenes (one thought is to separate opx & cpx)
- clays
- calcite
- hailte
I feel much more confident about the longer list of minerals we’re going to look at in thin section & hand sample, so I’ll leave that in the drawer.
Pyrite. No, seriously. I think it’s worth it to talk about a sulfide, if only for the environmental issues associated with mining. (And you should know I’m a big silicate fan myself!)
Or kyanite. You’re a metamorphic petrologist. Aluminosilicates are pretty and useful and have the nicest P-T diagram.
I think I would vote for magnetite, which is a very common accessory mineral. The important rock-forming mins look pretty well represented in your list, but I’d bet after quartz, the feldspars, and calcite, there are very few minerals as ubiquitous as magnetite. It’s not as abundant as some others, but it seems to show up everywhere as a percentage or two.
I agree both magnetite and pyrite are important minerals. Mt is found in a lot of systems, which makes it important.
Both of them have a lot of geobiology ramifications, so I feel like that is an important angle.
There is also a case to be made for dolomite, which some people believe is strictly produced by microbes.
I agree that dolomite should at least be an honourable mention, with its limey friend. About microbial dolomite: I don’t believe in concepts like ‘always’, ‘strictly’ or ‘never’ in geology :), but even so, that’s just primary and early diagenetic dolomite. I don’t think you can invoke microbes in massive replacement during later diagenesis, or in hydrothermal dolomitization.
Perhaps dolomite is a reminder that there are still a great many things we don’t understand, even in what students might think was established, fundamental geoscience (possibly because their professors don’t always reveal the uncertainties, but that’s another story).
My first thought was definitely one of the Al2SiO5 family.
Lots of your students might go off and study sedimentology, or work in a soft-rock industry like hydrogeology or oil and gas. Alongside the minerals you already cover, the most important missing ones are dolomite, kerogen, and pyrite. Dolomite is a fairly simple extension of calcite. Kerogen is best left to a bio-geochemist. That leaves pyrite.
Apart from the environmental issues Kim mentions, pyrite is an important mineral in early diagenesis, with interesting relationships to porewater chemistry and organic carbon. It’s also important in reservoir evaluation methods like geophysical logging because it is very dense and it conducts electricity.
It also gives you a chance to crack out the reflected light microscopes!
So I agree with Kim: pyrite FTW!
Maybe you could group biotite and muscovite (micas) and have pyrite *and* magnetite.
Seconded. Pyrite is a must for identification and it includes sulfides, while magnetite is important in the creation of all three rock types and geochronology.
I like the idea of grouping the micas and freeing up another spot. When I interviewed for a position as Earth Systems Curator at the Museum in Edinburgh one of the questions I was asked after my talk summarizing my research was my thoughts on the fact that the name “biotite” was no longer valid. My reply was “isn’t it? It is still pretty commonly used by metamorphic petrologists.”
I agree that you should include kyanite/sillmanite/andulsite for the opportunity to talk about phase diagrams and the fact that the same elements can combine to make very different crystalline structures.
I also agree that both pyrite and magnetite are worth including because each have properties which make them EASY for beginners to identify as well as both being rather common secondary minerals with important associations. Good luck choosing between them.
My first thoughts on looking at the list were that there were no ore minerals and no sulfides. So pyrite came to mind immediately.
But I think a good case can also be made for the pairing of magnetite and hematite, because of their relevance to oxidation state in the rocks and because they’ve been so important in Minnesota’s geologic and economic history of iron ore mining in northern Minnesota’s Mesabi Range. And you’ve got the banded iron formations up there which are just so cool.
I think the base of the list came from Darby Dyar’s list and my bet would be muscovite & biotite are segregated due to the fact that both of them appear on Bowen’s reaction series. Originally, anorthite & albite were both on the list, but I condensed them down to plagioclase this year.
I love kyanite / sillimanite / andalusite, but since they are only found in basically Al-rich metamorphic rocks, I find it hard to put them on the list. And I tend to talk about polymorphs with relation to quartz, so I’ve got that idea covered to some extent. Plus, my favorite mineral weaseled its way onto the list, so I’d feel guilty about adding another one of my personal top 5’s 🙂
On the dolomite issue, its grouped in my mind along with calcite (what can I say – I’m a met pet who plays with pelitic schists?).
Jennifer on twitter suggested serpentine, but its with the clays in my personal view of overarching mineral groups.
Anne’s logic of including magnetite & hematite hits a strong note with me and obviously, there’s quite a bit of encouragement to add pyrite to the list. I’m tempted to combine muscovite & biotite and add both suggestions.
Then you’ll have to group feldspars (!) so you can have kyanite-sillimanite-andalusite (I love kyanite), and still have magnetite-hematite-(with menion of goethite, the “common” iron-oxide, also present in the Iron Ranges), and can also still have pyrite, a common mineral. That would give you several ore minerals to talk about! (Kyanite in VA, some clays, pyrite at least as an association in ores, magnetite and all iron-oxides, halite, garnet at least for gems, and quartz or silica in sandstones/quartzites, and calcite in limestone.)
Missed your comment, Elli, while composing mine! 🙂
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