A few rocks of interest

[shivan]

G'day all, have a small group of rocks I picked up at Kangaroo valley that have me scratching my head a little. Anyone seen any like these?


The first has some interesting marking on the top. When I first picked it up I assumed it was from forming around crystals and minerals, but when I looked a bit closer it almost looks like leaf or branch patterns. Some of the darker bits have quiet a bit of detail when looked at under a loupe.






The next appears to be petrified wood on the outside top, but on turning the rock no growth rings are seen and it almost seems like flow banding is present. The bottom seems like there are sticks?







The next piece seems like coal in a few places, but seems to have pieces of petrified wood all through it, these shine in the light for some reason, but definatly wood grain under a loupe.







This was though to be petrified wood, but iam thinking it may just be a piece of rhyolite?






This piece again I picked up first thinking of petrified wood with what looked like borer holes, but after cleaning they seem more like flow banded or squished minerals?





This one stands out a bit more when wet, with a light blue, black and red bands. Top layer seems to be a jasper.





Next bit just seemed like a bit of quartz, however the top and bottom appear to have what seems a little like wood grains as oppose to crystal growth.




The last rock, I first though was a cluster of thin crystals, but am now wondering if it is the petrified remains of a fibrous plant? It seems from looking at the top and bottom that the little tube structures were hollow.

 

[Heatho]

Got no idea Shivan but they certainly are interesting.

 

[aussiefarmer]

The rock with the patterns on it looks like a fern or a broad leaf plant I say if you look around you should nearly be able to match it up with a plant in the area. Interesting rocks indeed

 

[grubstake]

The first one looks like crinoid (sea urchin) fossils to me (I'm not an expert but):
Images: http://tinyurl.com/qdorbaq
Details: https://en.wikipedia.org/wiki/Crinoid

 

[richo966]

petrified wood may be

 

[shivan]

Thanks for the input guys. I had wondered about a crinoid inprint on the first rock, as we have found a few fossilised stems around the place, but it does not look like any photos I have seen. The other interesting thing is the rock is igneous rather than sedimentary.

 

[Tathradj]

I think you have the bottom layers of either an ancient pyroclastic flow or
the impact area of a volcanic bomb.
Apart from a couple of your specimens they look like pieces of baked plant material.
Still very good conversation pieces.

 

[AtomRat]

To me most are results of lots of movement. I certainly know the quartz pattern is from 'shearing' when it slides on another rock along a fault line. The others to me seem like another form of axis shifting for strange shapes. I have a rock a geologist looked at one day with a broken quartz vein that the geologist mentioned had been rotated and broken several times to make its odd look

 

[AtomRat]

Also photo 10 / 11 reminds me of some hydrothermals I've seen too if that helps at all but its surrounding matrix was eroding

 

[shivan]

G'day AtomRat, I had not thought about slickensides for the marking on the quartz, but having a quick look the lines are in slightly different alignment on either side.

Tathradj, I would say you are right about the pyroclastic flow, I believe parts of it are exposed on Cambewarra mountain and erode into the creeks and river from there.
These few rocks just stood out as different from what I had found and had me interested 8)

 

[richo966]

I think atom rat is right

 

[AtomRat]

Different alignment could just mean separate rock sheering at different forces like when an anticline / syncline forms or a dyke pushes through

They certainly all have a unique charm and would have ended up in my bag which seems to break everytime on the return journey..