[Rockhounds] mystery mineral

Thu Mar 26 04:35:50 PDT 2009

Hi pete,

Since it is  transparent and light colored, I would assume that the streak
is white?
You didn't provide any information on the lustre so I left that out of the
equation.
Not really a problem because "transparent" rules out "earthy, metallic,
submetallic". 
2 by 1 inch is fairly large for most mineral species with gem clarity, isn't
it?

Could it be  danburite?

There are some candidates for the job:

DANBURITE: http://www.mindat.org/photo-9477.html
Awfully large X to give away unless donor didn't know what it was... S.G. is
closer to quartz.

FORSTERITE: technically possible but I doubt it... too large, too
transparent, also heavier than quartz.

ZOISITE: http://www.mindat.org/photo-89466.html , however: S.G. is 50%
greater than quartz with which you compare it.

Remotely : DIASPORE from the Turkish Selçuc locality? Still, 2 inch is VERY
big and diaspore has a S.G. of about 3.3 which is almost 50% heavier than
quartz. I assume you would have noticed that ;-)))

Cheers
Axel

Axel Emmermann
European Regional Vice President of the
Fluorescent Mineral Society
<http://www.uvminerals.org/>
=========================
Mineralogische Kring Antwerpen/Antwerp Mineralogical Society
<http://www.minerant.org/index.html>
Werkgroepleider/Workgroup leader: Fluorescerende mineralen/Fluorescent
minerals
Technische Realisaties/Engineering
My website:<http://users.pandora.be/axel.emmerman/home/>

> -----Oorspronkelijk bericht-----
> Van: rockhounds-bounces at lists.drizzle.com
[mailto:rockhounds-bounces at lists.drizzle.com]
> Namens Pmodreski at aol.com
> Verzonden: donderdag 26 maart 2009 6:00
> Aan: rockhounds at lists.drizzle.com
> Onderwerp: [Rockhounds] mystery mineral
> 
> How about if I get off this rift zone that we seem to be kind of stuck in
> for the time being, and ask something about a mineral?
> 
> I've got one that is really puzzling me.  And I'm not sure if it's  really
a
> mineral--it could be something synthetic, or just glass. Perhaps  someone
on
> the List may have ever seen something similar, and have some good
suggestions
> for me.
> 
> This is something I came across amongst a bunch of very assorted
specimens,
> given away by the Colorado School of Mines geology department several
years
> ago; I was looking through the material, picking out specimens either to
give
> away to teachers, or to save for my own use in classroom demonstrations
and
> seminars for teachers.
> 
> This one, this "crystal" (it looks like a crystal, but I don't know if it
> really is) is rectangular and blocky, about 2 inches long and about an
inch
> diameter (it weighs about 100 grams), and is pale yellow.  It is
completely
> clear--transparent--internally, but the outside has kind of a slightly
frosted
> appearance all around, as if it has been tumbled around a good deal.
There  are
> a great many chips on the edges, and all show a conchoidal fracture--no
> suggestion of cleavage in any direction. In overall  shape it would be
called a
> rectangular prism; the major sides are at right  angles, and the top is a
flat
> (basal) termination.  The base is  irregular.  One side has an additional
> "prism" face at about 45 degrees to  the others, and one corner also has a
beveled
> face at what appears to be 45  degrees; if these were all true crystal
faces,
> their miller indices would  be 001 (the flat top, "c" face), 100, -100,
010,
> 0-10, and these last two,  110 and 111.  Two of the main prism faces are
quite
> flat, but the other two  (adjacent, not opposite faces) are not really
flat at
> all, but kind of  irregularly rounded or "hummocky" (plus a lot of
> chipped/broken areas).  I  don't see any bubbles or inclusions in it of
any kind; it all
> seems to be clear  and gem-quality.  The "crystal" is hard--a knife won't
> scratch it, and a  quartz crystal doesn't readily make a mark either.  It
feels
> about the same  weight as an equivalent piece of quartz, and it is not
> fluorescent.
> 
> I've seen a lot of strange minerals and things that were not
> minerals--people bring them to me all the time--but this doesn't quite
look like  anything
> familiar.  It has the general shape of an orthorhombic crystal,  but is
somehow
> just doesn't look "right" for being a real crystal.  The  lack of cleavage
> rules out gem-quality feldspar, or topaz.  I've seen lots  of glass; if
this were
> glass, or quartz, someone must have cut it into the  rectangular shape (an
> odd shape to cut it into), and then put it somewhere (a  riverbed?  a
tumbler?)
> where it acquired a frosted surface.  And if it  were glass, I should be
able
> to scratch it readily with a sharp quartz crystal  point, which I can't.
> 
> Does this description ring any bells for anyone?  Yes, I'm one of  those
> people who is always (well, sometimes) telling other people to "go carry
out
> simple tests on your specimen, such as hardness", so this is their chance
to  tell
> me to do the same thing.  I have a balance set up to measure specific
> gravity so I'm going to do that--I suspect it will come out similar to
quartz.
> Does my description sound like any particular kind of gem cutting  rough
that
> some of you may have seen?  Or (but I don't really expect this  to pan
out), does
> it remind you of a crystal of any real mineral that you have  seen, that I
> may not be thinking of?  I can't imagine what it could be, if  not quartz;
I
> don't think it could be topaz (specific gravity will confirm  that), and
it's
> surely not beryl or apatite; nothing hexagonal looking about  it.  If it
were
> just a tiny crystal I'd be more inclined to think it was  "real", but,
something
> this big--doesn't seem likely.
> 
> I haven't had a chance to take any pictures of this, but once I do, I can
> forward one to any who'd like to see it.  And I'll see what the specific
> gravity shows.
> 
> Let me know if you have any great ideas about this, thanks,
> 
> Pete Modreski
> 
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