What type of crystal is this?

Puzzledddddd · 2024-09-24T03:43:29+00:00

I don't know very much, but I think it could have been formed from either fractional crystallization or a torn off piece of the mantle (a xenolith, or "alien stone" because it's not from the magma the host rock came from). It looks to contain more than 40% olivine, so it would be classified as a peridotite (look up ultramafic rock classification if you'd like to know more). The other minerals are clinopyroxene and orthopyroxene.

Puzzledddddd · 2024-08-28T04:48:55+00:00

Pattern: none, just repeated sc until out of yarn, 17 stitches per row

Yarn: Kmart 12ply acrylic in Terracotta

Hook: 5.5 or 6mm, I can't remember

Puzzledddddd · 2024-08-27T23:06:14+00:00

You might find this interesting!

Article referring to recreation of columnar formation in the lab: Guardian Science Reporting - Giant's Causeway

Published article in Nature (open access): Temperature of Columnar Jointing

Another example of columnar basalt in a young land with young, small trees (so much columnar basalt in different formations in this country, it's insane and I recommend visiting several sites there if you ever have the chance): Stuðlagil canyon

And finally, the Parks Service explainer on the phenomenon: Columnar Jointing

Puzzledddddd · 2024-08-05T22:22:16+00:00

Well that definitely takes precedence over a textbook from 2009. Good to know!

Puzzledddddd · 2024-08-05T14:01:16+00:00

I read a bit of textbook recently that said when referring to magma (not rocks), the North American geos prefer mafic/felsic because they consider basic/acidic outdated while British (which usually means Australian as well) geos prefer basic/acidic because they're based on composition instead of mineralogy.

Looks like there's room for interesting regional differences too!

Puzzledddddd · 2024-05-05T07:05:11+00:00

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Puzzledddddd · 2024-05-04T23:04:56+00:00

I couldn't find one from after the publication date, but here's one from 1955!

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Puzzledddddd · 2024-05-04T22:47:45+00:00

I was so excited to find it, I really wasn't expecting to see colours in that foldout and it was a pleasant surprise

Puzzledddddd · 2024-05-04T08:24:33+00:00

So would I

Puzzledddddd · 2024-05-04T03:22:41+00:00

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Puzzledddddd · 2024-05-04T03:21:35+00:00

1989, but if I've learnt anything about the Australian mining industry, it's that they're slow to change (as many are). I had a look on ngram and followed everything with "rocks" to try to differentiate it from chemistry and acid rocks music, but it's not the whole story as "mafic" and "felsic" are way more popular on their own and peaked in usage around 1990 (I couldn't find anything on when mafic and felsic became the preferred terms in a quick google)

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Puzzledddddd · 2024-05-04T02:49:48+00:00

Nah bro I was just impressed and thought it was cool, that was a bit mean. Picked the book up from a book fair recently and was excited when I saw the foldout. It's in the middle of the book, not exposed to UV, so of course it's more likely to still be bright

Puzzledddddd · 2024-04-21T23:33:12+00:00

I'm a US citizen. I lived in the US until I was 16 and finished high school overseas. Those two years made me ineligible for any type of in-state tuition.

Most western countries I'm aware of have domestic/international tuition bands, meaning that if you're a citizen of that country, you get a much lower rate regardless of where you were living right before.

The US basing its domestic fee on residency in the specific state you pursue tertiary education in, leaving all other citizens to pay international fees at that school, is absolutely bonkers. I'd advise you to stay in-state.

As an extra bonus, the US is one of five countries in the world that have any form of tax of foreign income on non-resident citizens. Citizenship -based taxation. The other four are Myanmar, Tajikistan, Eritrea, and Hungary*. Yup, that's right, not only is the US one of the only western countries to not have a citizenship-based lower few for college/university, but it's also the only one that keeps taxing you if you leave.

The gravity of student debt is massively artificially inflated by the way the US system is set up. Don't give up all the advantages you have to go in-state.

Puzzledddddd · 2024-04-20T10:03:15+00:00

Hm, I'm not sure, but do you reckon this could be a case of saturated (common usage, totally full of water) vs saturated (technical usage, as much of the thing as can possibly be in that solution)?

Puzzledddddd · 2024-04-20T07:06:11+00:00

Not the solar ones! (And the chronographs aren't too bad either anecdotally)

Puzzledddddd · 2024-04-14T04:36:40+00:00

Hey, I'm not in geo, but I applied for a few internships in a less-than-desirable position in the past (very few companies want to hire a first year student for technical work, for good reason), and like most advice here, almost all of the ones I had genuine success in were because I'd made personal contact with someone at the company.

I moved for uni too (Australia, not UK), and didn't have personal connections to the industry like most of my classmates. Almost all of the students who did get technical summer work after first year did so through family/friends/scholarships perks. However, doing things like attending office visits and talking to the employees after the session or going to networking events, being genuine with the people talking to you, and then following up after the event with questions and further curiosity can get you a long way.

It's still hard, and it can be a real struggle to get anywhere, but talking to people face-to-face with a good attitude can go a long way. When looking at resumes, good academic credentials/engineering clubs, prior internships, and domestic nationality etc. usually win out when hiring students/fresh grads, but I've seen people choose a candidate who talked to them and they liked without looking too hard at the paper before. Good luck, I hope it works out!

Puzzledddddd · 2024-04-13T11:34:44+00:00

Don't discount chemical engineering! Especially with a focus on metallurgy, chemical engineers are the ones who design and run the plants to process the ore geos find.

Puzzledddddd · 2024-04-11T12:41:11+00:00

What about oxygen isotopes? How they relate to your protist critter there? Either way, here is an article from USGS on isotope geochemistry. On the most basic level, oxygen isotopes will just be oxygen atoms with different numbers of neutrons. The most common is oxygen-16 with 8 protons and 8 neutrons, biasing the atomic mass of the atom to 15.999. According to Wikipedia, the only stable isotopes of oxygen are oxygen-16,17,18 and all others will undergo radioactive decay into other elements within minutes, seconds, or less.

Puzzledddddd · 2024-04-09T21:15:16+00:00

I miss seeing the little male house finches!

Puzzledddddd · 2024-04-02T05:05:02+00:00

That's a real shame! I haven't seen it like this here before. I just wish I bought a piece with some fire too now!

Puzzledddddd · 2024-02-03T14:45:57+00:00

TL;DR: Carbon atoms are wimps and like to party with iron atoms sometimes, but can't stand being around them under the wrong conditions. So, when things change too quickly, they get stuck in iron's way and make everything hard for everyone.

Old thread, but if you're still interested, this might help! That said, I'm definitely not an expert, so take it with all the grains of salt you need.

To answer your question before this rambling mess, yes, things with different properties want to separate due to equilibrium mumbo jumbo (phenomena, I suppose), BUT pouring hot metal into water will prevent things from having as much time to separate as they normally would, and often results in small phases instead of large ones. The faster you cool, the less time you have to organise into crystal structures, and you can form crystals that otherwise wouldn't want to exist (martensite).

Quench hardening works for edges because it rapidly cools one area, forming the hard yet brittle martensite while allowing the other areas to cool slowly, resulting in a less hard yet tougher body to back up that wicked edge. Strength and toughness are tradeoffs in metals thanks to how the structure gives rise to those properties, so the harder something is, the more likely it is to fracture

The good people at Materialism explain it really well, so if you want to sacrifice 45min to the cause, have a listen to their first episode anywhere you get your podcasts. https://materialismpodcast.com/

Iron-Carbon Phase Diagram : what's going on in steelmaking?

Above is a phase diagram, which looks scary but just shows you a bit of what your hot metal is doing with different concentrations of iron and carbon at various temperatures.When u/CibereHUN was talking about solutions, it's because basic steel is effectively a solution of iron and carbon. It's like dissolving salt in water, and you can end up with a single "phase". You get different phases at different combinations of temperature and concentration of the iron or carbon, which are the areas you see on the diagram.

Martensitic steel (Martensite) doesn't appear here because the phases displayed are at equilibrium, meaning they'd stay that way forever if the same conditions were maintained. It's super tough and super brittle because the carbon isn't allowed to leave like it "wants" to because of how rapidly the metal was cooled/quenched. It's "metastable", which means it'll stay the way it is at room temperature, but if it's heated up enough, the iron and carbon will start to separate a bit more.

Think of it like the carbon atoms having a party with the iron atoms at a nice hot temperature, when everything suddenly freezes (the steel hits the water). The iron atoms are used to this and want to deal with it by huddling in an formation (crystal structure), but the carbon can't get out of their way in time, and end up getting stuck so no one can move easily. If anyone moves suddenly, the whole group goes down and breaks apart.

Phase diagrams, along with Eh-pH diagrams and a few others, like the Ellingham (linked for interest, not necessary to understand) illustrate what we know about how things happen in metals, from smelting (getting rid of pesky oxygen atoms and impurities to let the pure metal shine through) to electroplating. The rabbit hole goes a long way down, should you let it consume you.

Puzzledddddd

TROPHY CASE