and progress plods along

[kareina]

...or perhaps "fits and starts" would better describe it. As I mentioned earlier today, I happily wiled away some hours playing with art in the name of science, until I finally realized that I could procrastinate no more, that the day was fading away and I'd not yet begun the task I'd set myself for the day. I understand why I was delaying, it is actually a scary thing to decide to base one's calculations upon an *estimate* which one makes *visually*. But since the chemical (XRF) analysis made by crushing a bit of this sample and sending it off to the lab is clearly not representative of the thin-section cut from the same rock (as can be told by comparing the estimates of what minerals should be present and at what composition with those which are there--indeed, the huge garnet present isn't even possible if the entire rock was the composition measured from that bit of powered sample). So it is is clearly time to try another technique.

My first attempt at visual estimating the amount of each mineral present resulted in a calculated whole-rock composition which is very, very similar to that obtained via the XRF analysis for most of the elements (ok, oxides). But three of them were *very* different. One of those, MnO, *needed* to be different--the XRF whole-rock composition had it so low that it shouldn't be possible for there to be this much garnet in the sample (well, at least not if it has this composition). I'd already determined that MnO needed to be at least three times higher for this much garnet to be present, and, indeed, my visual estimates resulted in it being about three times higher. This is encouraging. However, the results of the calculations predicting what minerals should be present only came out a tiny bit better than that obtained with the XRF whole-rock analysis.

Tomorrow I start playing with limiting the amount of H2O available for reactions, to see if it helps. Today I managed to write up 549 words for the thesis and create three new tables/figures to illustrate them, basically summarizing (a bit more technically) what I said above. So little progress, when what I want to be doing is finishing the writing, but without the calculations,there is naught to say, so the work goes on...

But now it is late (How does it get to be so late, so quickly?!) and I want to go for a walk before doing yoga and heading off to sleep.

Comments

[sismith42.livejournal.com]

it is actually a scary thing to decide to base one's calculations upon an *estimate* which one makes *visually*.

What about doing a sensitivity analysis on this estimate, so you can get a feel for what happens if your a few % off in your estimate?

[kareina.livejournal.com]

Funny you should mention that--having done the one set of graphs based upon that estimate, my plan for today is to try adjusting one mineral at a time up and down, to see how it changes things...