kareina

From broider_barones

1. Would you like to reign again? What was the most fulfilling part of reigning?

Yes, I think that it has been enough years now that I would like to reign again. I was so very young and new to the SCA when I served as 2nd Princess of Oertha that I didn’t really know what I was doing, and couldn’t properly appreciate it. I think I now have sufficient experience to more fully embrace the role. Which is funny, because for most of my time in the SCA I’ve had a champion carrying my favour in tournaments, yet I didn’t really want us to be granted victory—I was simply content with getting (or giving when it was me in armour) the salutes before each round of combat. Now that I feel confidant enough to seriously consider it I not only have no one carrying my favour, but I’m not even eligible to enter in my Kingdom of residence as I’ve not yet attended enough in-Kingdom events to meet the minimum qualifications. Therefore it isn’t going to happen any time soon!

It is hard to say what the most fulling part of reigning is—it has been so many years that my memories of being princess are a bit spotty. But I will never, ever forget the joy that came from making Kylson and Anne a Viscount and Viscountess, nor will I ever forget the tears in Kylson’s eyes when we gave him a Leaf.

2. Other than fiber and dance - what hobby do you like to spend time doing?

I love my daily yoga practice—it feels so good to move and to stretch. And there is something so very joyful from the balancing poses; knowing I can do a head-stand is an amazing confidence-booster! I love hiking and long walks. I really enjoy climbing, too, but haven’t made time for that one if far, far too long. My other weakness is reading. When I was young it was always SciFi/Fantasy books. These days LiveJournal, FaceBook, and blogs compete with fiction for my reading time.

3. What would be your ideal job?

One where they pay me to learn interesting things and have fun doing field work in the mountains and then play with fancy high-tech equipment to analyse the samples afterwards. One where I get to set my own hours and choose my own research topics. Plus or minus teaching. Yup, I like academia.

4. You could only go to/stay in 1 country for the rest of your life. Which one would it be?

I am so not a monogamist! But if you are going to remove everywhere else from the map I guess I’ll choose Norway, as it has a very good mountain to flat land ratio, is far enough north to have good weather, the vegetation is “right” to my Alaskan eyes, and they speak a language which is high on the list of languages I wish to learn. They are, sadly, lacking in an SCA branch, but I’m willing to play some other re-enactment game if I must (since the SCA would cease to exist when the other countries vanished anyway). Food might be an issue though, since I think a reasonable amount of food there needs to be imported, and if the other countries vanished, where would it come from?

5. Why garnets?

1. They are pretty!
2. They are very common in a wide range of metamorphic rock types
3. They are stable across a reasonably broad range of pressures and temperatures of relevance for metamorphism
4. The often form “porphyroblasts” (crystals that are noticeably larger than those which surround them)
5. They are easy to identify in hand-samples—their nice “garnet-red” colour often contrasts with the other minerals in the sample
6. They are easy to identify in thin-section—they have a high “relief” (they look like they are taller than the things next to them, even though they aren’t) and they are isotropic (they are black when the polarizing filters are crossed, no matter how the stage is turned, making them stand out against the bright blues, pinks, and yellows that the other minerals turn when the filters are crossed)
7. They have a rather broad range of possible chemical compositions, with iron, magnesium, manganese, and calcium all fitting into the same position in the crystal structure (this is part of what gives it a broad range of stable temperatures and pressures) and aluminum and silica can do a certain amount of swapping one for the other as well. There are a handful of other, less common elements which can also substitute for others in its crystal structure.
8. They have very slow diffusion, which means that once they reach a certain size the center of the grains no longer get involved in chemical reactions. As a result it is normal for the composition of garnets to be “zoned”, with the center containing more Mn than the rims, and the rims containing more Mg than the core (each of the other major elements also typically change their concentration from core to rim).

We metamorphic petrologist talk about the garnet cores being “armored” by the rims. The rims are, in theory, in equilibrium with the matrix minerals at any given time—this means that the minerals present will be participating in the chemical reactions that are causing the growth of some minerals and the dissolution of others. For many minerals the normal grain size is small enough that the reactions involve the entire grains, but garnets often grow large enough that only the outermost shell is involved in the reactions, with the inner portion “freezing” in whatever composition was stable when it was the outer portion.

So, just like an EverlastingGobstopper (do they still make those candies?) changes colors as you suck on it, so garnets show a range of compositions from core to rim. Part of the changes in garnet composition are due to rare ingredients having been used up making garnet (plus or minus any other zoned minerals present). So Mn, which tends to prefer garnet to any other mineral in metamorphic rocks, starts out “high” in garnet, but there is usually so little of it available in any given metamorphic rock it is soon used up and the garnets have gradually less and less Mn as they grow, until eventually the outer portions have no measurable Mn at all. The other reasons garnets change their composition is due to changes in pressure or temperature. Different recipes of garnet are stable at different pressures and temperatures. So if the conditions change different types of garnet grow on the outside of the pre-existing garnet. These features all combine to make it a very well-studied mineral because of all of the information one can extract about the history of the rock.

Note: today's icon is a Back-scatter Electron Image (BSE) of a garnet. It is a grain about 2 mm in diameter.
With BSE images the heavier the elements present the brighter the image, and the lighter the elements present the darker the image. The contrast for this image has been adjusted to make the garnet (which contains the reasonably heavy elements of Fe, Mg, and Mn) grey and the quartz (which contains only silica and oxygen) black. The two bright white patches are inclusion of monazite--a mineral which contains the even heavier elements of uranium, thorium, and lead (which the first two radioactive elements decay to). The pattern of black dots in the garnet are inclusions of quartz which got trapped inside of the garnet as it grew. The fact that there is ab obvious ring of quartz around the middle tells us that there was a noticeable change in the rate of garnet growth between the core and the rim. Indeed, when one looks at the composition changes of the garnet itself, there is a huge change in composition of the garnet which correspond to the change in the inclusion density.