[Rockhounds] Puzzle

[Earl R. Verbeek]

Hi Axel,

I looked that up, too, and since it's a pegmatite my thinking immediately
went to apatite.  The hexagonal form fits, as does that texture
perpendicular to the c-axis of the crystal that Carolyn mentioned, which
I've seen before in apatite.  From some localities it does somewhat resemble
the perthitic texture of feldspar.  Of course this doesn't fit the hardness
measurement, but in some cases, as Pete Richards discussed, it's not at all
a straightforward exercise to make a hardness determination.  Let's wait for
that photo!  And Carolyn, is the crystal sufficiently well formed that you
can tell us if the hexagonal shape is truly hexagonal, with six equal angles
and all prism faces parallel to the same axis, or is the crystal just
sort-of hexagonal in a broken cross section?

       Cheers-   Earl

-----Original Message-----
From: rockhounds-bounces at lists.drizzle.com
[mailto:rockhounds-bounces at lists.drizzle.com] On Behalf Of Axel Emmermann
Sent: Monday, July 13, 2009 5:48 AM
To: 'Rockhounds at drizzle.com: A mailing list for rock and gem collectors'
Subject: RE: [Rockhounds] Puzzle

Carolyn,

I looked at Mindat to find the inventory of the Havey Quarry. It turns out
that there are Havey Quarry #1 and #2 listed as well as the Berry-Havey
quarry.
In the latter there is bertrandite to be found. 
You didn't mention the size of the crystal. If it's not too big, bertrandite
would be a possible. It's not hexagonal but it can sometimes appear to be. I
have no idea how much experience you have (for all I know you may be a
professional geologist ;-)))
If this http://www.mindat.org/photo-236703.html was sitting on a matrix in
the shown position it could fool me for a couple of minutes.
This one looks even more hexagonal : http://www.mindat.org/photo-14746.html
Even more misleading: http://www.mindat.org/photo-148802.html

Bertandite scores 6-7 on Moh's scale... close enough?
On the other h	and: if you managed to measure a hardness of 7.5 with some
confidence the crystal (probably more than one?) must have been sufficiently
large to do so.
One would also expect a greenish fluorescence rather than a blue one if I'm
not mistaken?

I think that the best guess is still feldspar, though.
A photo would take us a long way....

Cheers
Axel

 
> -----Oorspronkelijk bericht-----
> Van: rockhounds-bounces at lists.drizzle.com
[mailto:rockhounds-bounces at lists.drizzle.com]
> Namens Carolyn Reynard
> Verzonden: zondag 12 juli 2009 20:45
> Aan: Rockhounds
> Onderwerp: [Rockhounds] Puzzle
> 
> To the List: I have and interesting puzzle.
> 
> I collected the specimen at the Havey Quarry, Oxford Maine.
> 
> It is a crystal that appears to be common beryl as you can determine the
hexagonal crystal
> shape.  The hardness is
> 7.5.  The color is a warm light tan.  The matrix is feldspar.
> 
> What doesn't quite convince me it is a  beryl is a texture that looks
likes like perthite and
> runs the complete length of the crystal into part of the matrix and is at
right angles to the C
> axis. The feldspar matrix fluoresces at bright light blue with red
perthitic texture as does
> this crystal..
> 
> I am wondering if this specimen is a pseudomorph, with perthitic
microcline after beryl.
> Would the microcline replacement still retain the hardness of the beryl?
> 
> I believe this is the important question.  Certainly the crystal
fluoresces like the microcline
> but there is the problem of hardness being too great for a feldspar.
> 
> Nice specimen, just wish I could figure it out!
> 
> Carolyn Reynard
>