Granite planes and Mt Tibrogargan

Quoted text begins.magma originally deep below the surface slowly sorts
itself due to gravity, heavier components sinking and lighter ones
floating upwards
End of quote.

Hi Norman,

In theory! I guess no-one has been around long enough to actually see
it happen. Prof. Bowen modelled it in his lab and modestly called it
Bowen's Reaction Series:

http://jersey.uoregon.edu/~mstrick/AskGeoMan/geoQuerry32.html
http://www.skidmore.edu/~jthomas/fairlysimpleexercises/brs.html

I visited a quarry today and watched basalt being split to size.
It was fine grained and full of olivine crystals.
Not far away, another quarry has 'black granite' (gabbro) with large crystals
but no olivine. I believe the two quarry deposits are good examples of
formations derived from similar minerals, cooling at different rates
relative to depth of exposure.

Yosemite's Half Dome and its Diving Board reminds me of one of a series of
trachytic plugs near Brisbane. Mt Tibrogargan, also known as Gorilla Mountain,
fittingly overlooks Steve Irwins's Australia Zoo:
http://sunshinecoast.platypus.net.au/glasshouse.htm

Simon