What rock is this?

Hey guys

Just wondering if anyone could please help me out identifying this rock.

Located under an overhang from a very large slate and country rock cliff on the side of a mountain. A huge amount of quarts viens run through out the rock face as well.

Looks very interesting. Thanks for your help!

Nick

Looks like Basalt but I could be wrong....

Looks to me like the start of a limestone formation from the way it seems to run in a ribbon down the face of the stone. If you have a small piece there are a few tests you can do to narrow down which mineral it is.

Hi Nick, I think G wanderer is on the right track. I managed limestone caves in various areas for many years and the rock is definitely showing chemical weathering, etching and appears to have some precipitation minerals.

The section of rock may be a mineralised quartz vein... with the mineralisation likely to be pyrite.
When water hits the pyrite it will form acids that will dissolve the surrounding rock and create secondary minerals.

Because it is under an overhang it would be catching mineralised water percolating over the overhang or through the rock above. This mineralised water is probably dissolving the rock and precipitating minerals leached from the shale above.... evaporates/salt minerals. I can see the shine from a couple crystal faces? calcite/gypsum?who knows.

The grooved/cavity like features support the idea that the rock is being chemically etched from decomposing pyrite.

All the above is a guess... being based on the one picture.....a look at the fresh broken rock free of algae/mineral coatings is the only way to identify what is really happening or if there is some minerals in the rock causing the cavities/features.

Cheers RDD

Thanks for help guys and for the detailed response RDD. That was extremely helpful.

I came across it a few months ago and had never seen any rock like this before so I was very curious. It is good finding different things out there! Keeps you guessing that's for sure.

The rock that this is located on is really big and also hard to get to so it will be good to have a closer look to see what else may be around.

Might have to give it a few more months when all the brown snakes disappear.

Thanks again for all your help!

Nick

Yes I thought Limestone as well. If you put a small piece of it in a 50/50 H2O +HCL mixture and it fizzes it is a carbonate mineral most likely limestone / dolomite or marble.