[Jewelry making - Article 01207] - Re: [Orchid] Diamond question

[Michael . Hing]

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>     Since diamonds are formed in earth's magma 

    	Scientists are unsure about the exact formation conditions for
    diamonds: it is possible that they crystallise in liquid magma, but
    it is also possible that they crystallise in solid rock. 

>         	and pulsed to the 	surface through quick explosive eruptions
>     without changing temperature or pressure 

    	The pressure and temperature change enormously.  However, in a
    kimberlitic explosive eruption, the diamonds are blasted to the
    surface so rapidly that they cool down before they have time to
    metamorphose into graphite. 

>     	does anyone know how a minute crystal of red 	(ruby? garnet?) can
>     become imbedded in the diamond? 

    	The red crystal you see is probably garnet.  Ruby is also a
    possibility, but ruby inclusions are MUCH rarer than garnet
    inclusions (years ago, it was assumed that the red crystals were
    rubies but this has been shown to be incorrect in most cases). 

    	Basically, the diamond crystallises in eclogitic or peridotitic
    rock deep below the surface of the Earth.  As it grows, it can
    enclose small crystals of the minerals around it.  These can be
    various different types of garnet (usually reddish, violetish or
    purplish), or peridot (greenish crystals of olivine, forsterite,
    etc.).  The diamond crystal is then blasted up to the surface -
    possibly four billion years later. 

>     	As far as I've 	read, only diamonds and peridot come up from magma 

    	So do garnets, and several other minerals. 

?8-)
-Michael.


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