Any geologists in?

[RizzoTheRat]

Strolling down a New Zealand beach and I was amazed at the range of different types of rock. Obviously an area with volcanism, glaciers, sea, etc, so it makes sense there's some variety but can anyone tell me anything about this little selection?
I'm guessing the white is some kind of quartz but I've realised I know naff all about rocks. And what the hell is the really well defined triangle on the rock underneath?

Edited by RizzoTheRat on Tuesday 26th August 08:09

[Soloman Dodd]

That looks like Isoscelesium, the raw material for a flux capacitor.

[hidetheelephants]

It's from what the boffins call unconformity, which TL;DR is multiple stages of the same type of metamorphism(squeezing and heating at great depth in the crust) interrupted by movement of the plane of the rock through in this case what looks a lot like 120 degrees, then repeating it a few eons later. Not my subject but I did read a book about it a long time ago; google furnished this introductory text which sort of refreshed my memory.

[Arkose]

RizzoTheRat said:

Strolling down a New Zealand beach and I was amazed at the range of different types of rock. Obviously an area with volcanism, glaciers, sea, etc, so it makes sense there's some variety but can anyone tell me anything about this little selection?
I'm guessing the white is some kind of quartz but I've realised I know naff all about rocks. And what the hell is the really well defined triangle on the rock underneath?

Edited by RizzoTheRat on Tuesday 26th August 08:09

The lines would just be fractures in the rock, like when you hit something with a hammer it can caused conical / triangular shapes.. the white lines is where minerals have entered

[speedy_thrills]

Greywacke with banded Gneiss I think.

Greywacke is a type of sedimentary rock (sandstone) laid down by fine sediment falling to the abbysal plain over time. Gneiss is metamorphosised sedimentary rock.

I used to live in Wellington, NZ where you see a lot of greywacke formations. Lovely part of the world, would move back if the employment opportunities improved.

Edit to add: In the UK I think it's found in the outer Hebridean Islands.

Edited by speedy_thrills on Saturday 6th September 06:29