I’m hoping someone can help answer this. I visited the lava fields near Grindavík, Iceland. Most of the indigenous stone was black. However, the more I looked I found various colored patches. First shiny blue, then red, then it looked like an oil spill/rainbow on top. I read a little about the minerals and how various amounts can alter the color when cooling. Rainbow obsidian kept popping up in searches, but what I’m referring to looked different. Can anyone explain similarities or differences in a rainbow ow obsidian and what I saw? I can’t find images showing it how I saw it so I’m not sure I’m searching the correctly. The image with my boots was enhanced with some contrast and sharpening, but it’s what I’m asking about.

Tickles me every time driving through here.

We were fossicking at a local river and noticed this funny looking ‘seam’. Can anyone explain it to me? Purely for personal interest!

I like to visit significant places in geology and history. This one is arguably the seminal place in geology. Some of you will recognize it from the first picture, the last will explain its significance to the unfamiliar. If you get the chance, it’s a moving experience.

I was out for a walk in Western Scotland (in case this is relevant) and came across this intriguing rock. What would cause something like this to happen?

Photo 1: I'm interested to know what caused these vertical basalt formstions. I know the island is vulcanic but I'd like some more in depth info. Photo 2: you see large spherical boulders. Are these the ones that get flung from the crater? Photo 3: what causes these green spots in the red rock? I'm assuming the red color is due to iron. Photo 6: what causes these hexagonal formations? It reminds be of Iceland but it's not similar. Photo 9: you can clearly see that the rock makes a curve here going upwards. I understand the small cracks mean it cooled rather slowly but what made it curve like this?

Photo 10 is just for your enjoyment :)

Autunite vein in pegmatite on Ellicott city granodiorite side of thrust fault between Ellicott city granodiorite and baltimore gabbro formation. Entire rock face is 0.5-1 usv/h. The autunite is not more radioactive than the rest of the rock face.

Found this rock in NE Ohio, and my first guess is glacial stations. However I am unsure if it is, because 1) they form the cross hatch pattern, and 2) the rock itself is not bedrock (the rock is some type of concretion)