Geology Studyblr

Geoscience student in their final year, a good thesis is a done thesis.

[justbegneiss]

💫 Happy perseid meteor shower to those who celebrate! 💫

[hedgehog-moss]

I need to confess something—my last post presented a deceptively idyllic vision of my hike in the snow. I only posted photos from the tranquil walk home at dusk and neglected to mention that I (once again) got lost in a featureless expanse of snow and briefly became convinced I would never find the road again and would have to dig a little den like an Arctic fox to spend the night.

You see, there's this place where Pandolf really loves to go for a walk on snowy days—it's on top of this plateau here:

^ see the fence in the middle, that curves to the left? Nothing bad can happen as long as you follow it. There are lots of landmarks in this direction, like trees, more fences, and a couple of houses.

In the other direction, however, lies The Nothing.

Here's a photo of Pandolf (eagerly) standing near the edge of The Nothing:

Characteristics of The Nothing: it is vast, and white, and becomes more and more featureless the farther you go into it—

—and Pandolf really, really loves it.

Even when he falls into a surprise hole where the snow is suddenly three times as deep (another characteristic of The Nothing), he'll just push himself out in one great powerful jump and keep frolicking.

Or he'll remain in the spot where the snow is deeper and try his best to bury his entire self into it.

He sometimes gets crazy eyes in The Nothing.

We always start this walk with such good resolutions.

We're definitely staying close to the fence this time! With all the lovely landmarks on the left!

And then, inevitably,

Further notes from my studies: • The Nothing has some small plants and rocks, but using them as landmarks is foolish, as they will eventually disappear. • No matter how many foot-, paw-, and dog-headprints you leave and how deep they are, they will disappear before you are able to retrace your steps, probably because The Nothing is always so windy.

Pandolf thinks this is a great characteristic of The Nothing, as it means he never runs out of immaculate snow to dive into.

The wind and the resulting snow mist are the really treacherous things about this place. These photos were taken in roughly the same spot, a couple of hours apart. In the first one, the fence on the left is clearly visible; in the second one, it has started to melt into The Nothing.

There's always a moment when I end up standing in the middle of, well, nothing, with indistinguishable whiteness in every direction, under my feet, above my head, left, right, and I start thinking about writing poignant farewell messages in my Notes app for my family to find at some point in the future.

One last interesting thing about The Nothing is the way Pandolf reacts when I finally find my bearings again and start walking faster, determined to get back to the safety of the road before it gets dark.

Pandolf then just

It's very different than the playful, energetic way in which he normally buries his head in the snow. This second type of burying is clearly a form of protest—if I continue walking away Pan will reluctantly follow me for 20 or so metres, then flatten himself to the ground again, in the same despondent way.

Hypothesis #1: He is trying to play dead like a possum, hoping I will go "well, I can't lug a dead dog all the way home, I'd better leave him here." And then he'll stay with The Nothing forever.

Hypothesis #2: He is trying to lay as flat as possible so as to become all but invisible against the snow. It's unclear if he knows he is the wrong colour for this.

Hypothesis #3: He is trying to commune with The Nothing, burying words of devotion and friendship deep into the snow and promising to return soon.

Conclusion: I'm sorry, I know that's a very long post, but seeing as each of these photos depicts perfect felicity on Earth, I find it hard to delete any. I also like how I intended this post to be about my long disoriented trek through the snow, wondering if I was going to find the fence or the road again before dark—and then I got distracted by how happy Pandolf was. Which is exactly how I end up getting lost in The Nothing every single time!!

[woman-becomer]

shout out to the giant worm in the center of the earth. thank you for never surfacing 🙏 we appreciate you. have fun in the lower crusts

[thesquirrelqueer]

hadestown is “maybe it will turn out this time” but it doesn’t

& juliet is “maybe it will turn out this time” and it does

[thesecondface]

Started a second project (this one the mid atlantic ridge). Took a while sitting on online paint to fix a photo to cross stitch conversion so its accuracy is compromised somewhat. We live!

[tomundsen-deactivated20250731]

The Good Place 3x11

[dozydawn]

opalized plesiosaur vertebra

[hometoursandotherstuff]

[flowers-but-gay]

[iamthepulta]

Differences between pyrite and chalcopyrite? (With pictures?) 👀👀

Initial differences: Pyrite is FeS2. Chalcopyrite (creatively named) is CuFeS2. Pyrite is an almost silvery yellow on a fresh surface; chalcopyrite is more of a bronzy yellow. The difference is subtle, but once your eye is tuned, you can almost always pick out bits of chalcopyrite in a sea of pyrite.

The cleavage of the minerals helps too: pyrite almost always breaks with glittering sharp edges unless it's pretty oxidized or weathered. chalcopyrite is rough, almost like a smear. I think it's much closer to looking like gold, than real fool's gold, tbh.

It's really hard for a camera to properly catch that glint, but I gave it a shot:

This sample is a good 50/50 Py-Cpy, and I think the portions that look smoother are simply weathering from the sample being passed around. But you can still see Py is almost... brighter. And on the left, there's a very clear crystal of straight yellow Cpy that stands out.

This is more typical copper ore material. I think this sample was nearly all disseminated Cpy. Not great for differentiating the Py-Cpy color, but you'll see this all the time.

I just really wanted to talk about this one, lol. LOOK IT'S SO COOL IF BLURRY. I think it's an IOCG (iron oxide copper gold deposit type) massive sulfide sample. The bronze in the far lower left is Cpy, but the red in the middle is specular hematite (hematite that formed from hydrothermal solution rather than oxidized at the surface). The majority of the rock is magnetite, and I think some of the brassy-silver color in the center is pyrrhotite.

Pyrrhotite is pyrite one step to the left: Fex-1S. Because there's less iron, the Fe2+ has a very slight positive charge, just like magnetite where the Fe2+ offsets the charge balance of the other Fe3+ and S ions.

ANYWAY, this rock is nuts and I can't wait to cut it open and stick it under the microprobe~

BEST FOR LAST~

This is massive disseminated chalcopyrite, but it's been sitting in the drawer for 20 years, I think. Pyrite and chalcopyrite really pop when weathered. So the gold-brown is Cpy, and the silver 'clast' on the edge is Py.

-

Additional unnecessary but fun rambling about ore mineralogy:

Like, mineralogically I think the biggest difference is that Fe2+ is cubic and Cu1+Fe3+ is tetragonal so it can fit weirder stuff in. If you start thinking about the minerals as part of the whole, 1+/3+ ionic bonded and 2+ ionic bonded Things are the most stable position for metals to be in.

I love these minerals but whenever I want to describe them, the word that pops into my mind first is Evil. Pyrite and Chalcopyrite are fucking evil. xD

They're stable under a huge range of pressures, temperatures, and oxdiation/sulfidation states. Iron is 2+ in pyrite and 3+ in chalcopyrite, so you can substitute pretty much any 2+ or 1+ metallic ion in the Fe and Cu sites, and sulfur will happily substitute for any non-metal or metalloid.

This means you can have pyrite in your deposit, but it's pyrite with an abnormal amount of... idk, tellurium. And that will change the properties of your pyrite, but not pyrite itself. This is an 'abnormal impurity' until you form frohbergite, which is FeTe2. And BOTH do this. Both cpy and py are sliding scales for almost every single ion that fits.

So if you're trying to process chalcopyrite but you have a large silver impurity in the copper site, it might react poorly with the flotation chemicals we use to separate it from pyrite. Or maybe be harder to grind to the proper size, which will take up more energy. (This is gauged experimentally before they set up the processing circuit because that's a lot of money, and to some degree I'm exaggerating the effects. But a friend is also texting me right now asking how tellurium in pyrite will change oxidation rate, so impurities are a non-negligible factor.)

ANYWAY. Pyrite and chalcopyrite are fucking myths that should be abolished except they're fucking everywhere, so they never will be. Lol.

Chalcopyrite is more yellow. xD

.

(as the thermodynamic pressure of oxygen in the system increases, ((not oxygen content)), you'll have greater minerals of oxidation. i.e. Magnetite Fe2+Fe3+O4 has an Fe2+ where Hematite has Fe3+O3, its 3+ is at a higher oxidation state. Pyrrhotite is low enough that it's just Fe2+.)

[joemomrgneissguy]

HAPPY SNOWBALL EARTH WEEK!

If the entirety of Earth's history were a year, we have finally got to the Sturtian Glaciation in the latter half of the Proterozoic.

Lasting for a whopping 57 million years (4.6 days at this scale) there is evidence for the Sturtian Glaciation on every continent, and nearly as much coverage by the shorter lived Marinoan Glaciation (roughly 22.2 my or 1.79 days) that followed soon thereafter. The two collectively define the Cryogenian Period and stretch on our calendar from November 4th to November 10th.

My favorite deposit from this time is actually in Death Valley, CA of all places.

Image Credit: Marli Miller

Notice how there are these big rocks just in the middle of this really fine grained mudstone? How did they get there?

THEY WERE CARRIED OUT TO SEA!

As the glaciers reached the ocean, some of the rocks they plucked up were taken along with. When the ice melted, they were just left on the ocean floor surrounded by fine mud as a submarine glacial erratic.

Things really start accelerating on the calendar after this week, because next up is the Ediacaran.

[grittyghoul]

I made these petrography affirmations

[im-lost-in-ikea]

i love floor time (normal blood pressure)

[mineralsrocksandfossiltalks]

Monday Musings: Why are there so many perfectly preserved soft-bodied animals found in the Cambrian?

There are a number of ways to get the perfect preservations needed to fossilize soft parts but none of them are particularly common. On the other hand, most of them require water and there was quite a lot of it 518 million years ago.

Phosphatization occurs when large quantities of phosphate are present, either in sea water or from the tissues of a decaying organism. In some cases, microbes that fed on the tissue control the phosphatization. Many soft tissues are preserved this way in the Burgess Shale. The phosphate comes from the tissue itself and when pH is low and oxygen is absent, it becomes the primary method of fossilization.

Silicification is one of the most common ways to fossilize something because silicates is the most common rock forming minerals in the crust. Silica often replaces other minerals that have dissolved out such as calcite shells. This is usually seen to preserve things like trilobites. It doesn't often fossilize soft tissue.

Another form of preservation found at least in the Burgess Shale is carbonaceous film. This occurs when something is buried under several layers of sediment and diagenetically altered (in this case by heat and pressure brought on by compaction) and the animal lacks a hard skeleton or shell.

When we look at quarry locations on a paleo map,

and examine the rocks, we see that they lived and died in the right place at the right time (if the taphonomic and preservation bias don't lead us astray).

The Burgess Shale beds were deposited at the base of a cliff of calcareous reefs below the depth agitated by waves during storms. The most widely accepted hypothesis for burial is that part if the reef became detached, slumped and transported rock and debris several kilometers and quickly burying anything in its path.

On the other hand, the Maotianshan Shale was probably buried periodically under turbidity currents, basically an underwater mass wasting event. This is why we don't build our homes on old landslide deposits kids.

The Sirius Passet lagerstatte of Greenland was yet a different environment close to the boundary of an oxygen minimum zone according to geochemical analysis. It is thought that the original preservation was phosphatization that was later altered to silica by low grade metamorphism during the Devonian Period mountain-building events.

Finally, we have the Sinsk Biota of Siberia which inhabited an open marine basin where storms created back currents that sent many animals off into the oxygen depleted depths below. Anoxic conditions prevent growth of microbes that would normally decay flesh allowing soft tissues to preserve.

Now, it is also important to note that oftentimes, parts labeled soft tissue are not necessarily as soft as you believe. Take keratin for example which makes up nails, hair, feathers and sheaths over horns. It's not really that soft in some cases but it is softer than bone which makes it harder to preserve.

Whether we mean keratin or chitin (a natural polymer used to strengthen fungi and invertebrates) or internal organs which really are soft tissues, the Cambrian lagerstatten really are something else.

[geoledgy]

The volcanologist and the spirit medium.

[geologyin-blog]

A stunning polished slab of fossiliferous limestone

Photo: GeleryPetriefiedWood

[barghest-land]

kinda have no idea what im doing when im drawing ammonites but at least it's fun!!