Geology question, whats going on here.....

[tailormarc]

Hey guys, there is a location here in WA , place called Toodyay, about 100klm from Perth. Its known for some gold but i go to this one location to dig some nice quartz crystals. While exploring the bush i came across this. Not man made and stands out big time. I climbed it and dug midway up into it and at about 1 foot deep i hit a very fine talcum powder layer, the deeper i got it stayed the same, soft as and fine powder. Love to know how the hell its formed and what this burnt looking rock is on it. When i break the black rock open some of it has rainbow colors like it got super hot as some time. Found a chuck of quartz with hematite that was interesting so im assuming the black rock could be hematite .
Anyone know whats going on with this...
Untitled by Marc Russo, on Flickr

Untitled by Marc Russo, on Flickr

Untitled by Marc Russo, on Flickr

Untitled by Marc Russo, on Flickr

Untitled by Marc Russo, on Flickr

Untitled by Marc Russo, on Flickr

Untitled by Marc Russo, on Flickr

Untitled by Marc Russo, on Flickr

 

[user 4386]

I can only guess (despite you providing good photos). My guess would be something like a very high-grade metamorphic rock, a coarse-grained high-grade metamorphosed mafic (greenstone) rock now consisting pf things like large pyroxene and phlogopite (mica) crystals. What we might call granulite. The "rainbow" effect more likely formed during later weathering, and your "talcum" is probably clay formed by deep weathering.

 

[tailormarc]

I can only guess (despite you providing good photos). My guess would be something like a very high-grade metamorphic rock, a coarse-grained high-grade metamorphosed mafic (greenstone) rock now consisting pf things like large pyroxene and phlogopite (mica) crystals. What we might call granulite. The "rainbow" effect more likely formed during later weathering, and your "talcum" is probably clay formed by deep weathering.

Makes sense especially the clay part. Do you think with that kind of geology that there maybe other gems around. Lots of granite and quarts. A hill like this near by entirely made of quartz

 

[user 4386]

The other probably makes sense as well, as I have been there and looked at the rocks.

Gemstones can occur in granulites (eg rubies in Sri Lanka), but I am not all that familiar with Toodyay rocks. Probably not in those particular rocks in your photos.

 

[stonesaustralia]

But where is this area in Toodyay??