Anyone into rock?

Tringa

Tringa

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I'm hoping the forum has someone with geological knowledge.

The rock in the photos was not collected by me but I think it is probably from around Gairloch/Poolewe in NW Scotland.

Its density of about 4.6g/cm3. However, we had no scales that could take its weight so we estimated by comparing it to known weights and the volume was from a very crude displacement of water, so the density is only an estimate.

The dimension of the end shown in the first photo is 15 x 12cm and it is about 16cm high.

Most of it, as I hope the photos show, is very fine grained(which suggests rapid cooling) and our guess is some sort of basalt(which doesn't say much). However the more coloured end shows banding(a bit like gneiss) and larger crystals(which suggests slow cooling) of what look like quartz and feldspar.

Any views if our guesses about composition are correct and how there is one relatively small rock that shows both rapid and slow cooling of molten material.

Thanks

Dave

R1 by Dave Marley, on Flickr

R2 by Dave Marley, on Flickr

R3 by Dave Marley, on Flickr

R4 by Dave Marley, on Flickr
 
It's interesting, but as I know zilch about geology I'll watch this with more interest
 
Other than that the layering makes me think of sedimentation such as sandstone, though the grey rock looks like an igneous rock such as basalt.

If you find out more it would be interesting to see a more informed update:)
 
Tis a pretty rock, no doubt.

I know nothing about these things but my imagination came up with a series of eruptions and sedimentary deposits one after the other over time, then a final massive eruption.
 
Tringa said:
I'm hoping the forum has someone with geological knowledge.

The rock in the photos was not collected by me but I think it is probably from around Gairloch/Poolewe in NW Scotland.

Its density of about 4.6g/cm3. However, we had no scales that could take its weight so we estimated by comparing it to known weights and the volume was from a very crude displacement of water, so the density is only an estimate.

The dimension of the end shown in the first photo is 15 x 12cm and it is about 16cm high.

Most of it, as I hope the photos show, is very fine grained(which suggests rapid cooling) and our guess is some sort of basalt(which doesn't say much). However the more coloured end shows banding(a bit like gneiss) and larger crystals(which suggests slow cooling) of what look like quartz and feldspar.

Any views if our guesses about composition are correct and how there is one relatively small rock that shows both rapid and slow cooling of molten material.

Thanks

Dave

R1 by Dave Marley, on Flickr

R2 by Dave Marley, on Flickr

R3 by Dave Marley, on Flickr

R4 by Dave Marley, on Flickr
Click to expand...

It's called Gneiss, I have a number of rocks layered similar to that (not difficult to fine up here). One is flat, like the perfect skimmer, that's quartz on one side and granite on the other.

here's a linky
 
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