[Rockhounds] Crystal Puzzle Much Closer to Solution

[Axel Emmermann]

Carolyn,

I think this is feldspar!
Have you any of those amazonite crystals from Pike's peak? 
Or even better: http://www.mindat.org/photo-107763.html
If you rotate your specimen I believe you'll be able to match the angles
between the faces to that of the picture.

Cheers
Axel 

 

> -----Oorspronkelijk bericht-----
> Van: rockhounds-bounces at lists.drizzle.com
[mailto:rockhounds-bounces at lists.drizzle.com]
> Namens Carolyn Reynard
> Verzonden: maandag 13 juli 2009 22:33
> Aan: Rockhounds at drizzle.com: A mailing list for rock and gem collectors
> Onderwerp: Re: [Rockhounds] Crystal Puzzle Much Closer to Solution
> 
> Hi Pete,  One of the faces must really be a cleavage plane. You guys are
> great!  Don't be sorry about not explaining the Millar indices, that would
> require  diagrams!
> 
> Carolyn Reynard
> 
> 
> 
> 
>  ----- Original Message -----
> From: "R. Peter Richards" <rpr at heidelberg.edu>
> To: "Rockhounds at drizzle.com: A mailing list for rock and gem collectors"
> <rockhounds at lists.drizzle.com>
> Sent: Monday, July 13, 2009 4:21 PM
> Subject: Re: [Rockhounds] Crystal Puzzle Much Closer to Solution
> 
> 
> One further thought.  If your specimen is feldspar, it should show
> two directions of cleavage at right angles (or very nearly so); one
> of these is perfect and the other less so.  None of the other
> minerals that have been mentioned as candidates has more than one
> direction of cleavage, except bertrandite, which has four, one
> perfect ({001}) and three good (({010} and {110}, the latter with two
> sets of planes at 45° to the former).  Sorry, I'm not going to try to
> explain the Miller indices!  I feel quite confident that this is not
> bertrandite.
> 
> Pete Richards
> 
> 
> On Jul 13, 2009, at 1:37 PM, Carolyn Reynard wrote:
> 
> > Thank you Larry, Pete R. , Axel,  Earl & Pete M.,
> >
> > The one face of broken partial crystal in question  is 2 inches
> > long,  another  face is 1 7/8 inches wide.
> >
> > I have thought about all you have mentioned. I rechecked the
> > hardness with metal hardness points, but this time studying the
> > scratch under the microscope.  I certainly was wrong about the
> > 7.5..Clearly it is in the feldspar hardness range 6-6.5.  The
> > texture is finely perthitic without much doubt. I am very familiar
> > with the texture of apatite and I don't believe it is an apatite..
> > I have tried to measure the angle of the crystal with my antique
> > paper and plastic Penfield Contact Goniometer. The one angle I
> > believe I can determine is 44 degrees. Certainly not hexagonal.
> >
> > I have posted two scanned images on http://rockhounds.ning.com
> > Please go my page; Carolyn C. Reynard.
> >
> > I do intend to photograph the crystal this afternoon and post the
> > images. They should be better.
> >
> > I believe I fell into the trap of quick ID.  I listened to several
> > who identified it as beryl, all along I thought it must be feldspar
> > with the texture and fluorescence. I doubted.
> > Most likely that is why I was trying to put the two together in a
> > pseudomorph.
> >
> > I feel quite comfortable now that it  is a feldspar. What say all?
> >
> > Carolyn Reynard,
> > amateur geologist
> >
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> ___________________________________
> R. Peter Richards
> rpr at heidelberg.edu
> Morphological crystallographer
> 
> 
> 
> 
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