Identify this rock/mineral?

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Offline Bass

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Identify this rock/mineral?
« Reply #100 on: 18/11/2008 18:39:27 »
Now that I can see this on a decent monitor...

The green mineralis probably not idocrase (californite- or american jade), the color and hardness don't seem quite right.

My guess is still eclogite- an intensely metamorphosed rock containing pyrope, which is a distinctive red garnet, and omphacite- a unique green pyroxene.  Darker green probably another pyroxene- likely the clinopyroxene augite.  Eclogites form at very high heat and pressures (lower crust or upper mantle).

Less likely, but still possible, this may be contact metasomatic rock, or skarn.  Skarns form where carbonate rocks, such as limestones, come into contact with hot granitic rock.  The heat and fluids from the granite change the carbonates into new minerals- often garnets, pyroxenes and amphiboles.  If this is skarn, the red garnet is either grossular or andradite (though andradite is less commonly red).  Green is probably the clinopyroxene diopside.  Fracture fillings are likely calcite- wollastonite is more commonly zoned further out than diopside-garnet.
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