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Beautiful Bright Red Pyrrhotite(?) Crystal - Teesdale

Posted by Roger Curry  
Roger Curry September 14, 2014 01:06PM
Hi All,

I've recently been trimming part of a clay-ironstone septarian concretion. It's from the namurian shales exposed in Coldberry Gutter in Teesdale; the trimming was to better display its millerite spray (a similar millerite of mine - video here, Mindat discussion here).

The detritus from the trimming I examined under magnification. In amongst the kaolinite dust, odd millerite hairs and tiny sceptre quartz crystals, I noticed a flash of red. My cheap stereo microscope soon revealed something I'd never seen before...

A single, vivid red tabular hexagonal crystal, with a bright metallic lustre, around 0.2mm greatest dimension, and very thin. I think it's pyrrhotite.

It's a beautiful crystal, with only one edge showing a former point of attachment. The edges show modification from an ideal prism - i.e. there appears to be a chamfer around the edge. It's like the Pyrrhotite no.15 - Goldschmidt (1913-1926) diagram shown on the Mindat pyrrhotite page "Crystal Atlas" (although the Coldberry crystal is much thinner than this).

The photos above were taken through an eyepiece of my microscope with a hand-held 4 year old HTC Wildfire 5MP smartphone camera. Sorry about lack of focus, it's not an ideal setup!

Here's a video showing the diminutive size of the specimen. As you can see, it's presently stored wrapped in a cigarette paper. It's certainly the smallest specimen of any kind in my collection. And it's the only one I've found. I've always had a close look at the debris from trimming parts of my three millerite bearing nodules, found in the eighties, after smashing many, many Coldberry nodules. So it's rare at Coldberry, as far as I know.

Although the colour of the crystal nicely shows why the mineral was named (from the greek pyrrhos - red or flame), another characteristic of pyrrhotite, that it's magnetic, isn't apparent with this crystal. A strong neodymium magnet doesn't even budge it.

Since pyrrhotite isn't mentioned on the Mindat Coldberry page, I looked at the other occurrences of millerite bearing ironstone nodules in Britain. I found this reference from the National Museum Wales webpage on pyrrhotite here.

"South Wales Coalfield: pyrrhotite is an uncommon component of the septarian ironstone nodule-hosted sulphide assemblage, better known for its millerite specimens. Hexagonal platy crystals were recorded from Parc Colliery, Cwm Parc by Firth (1971), while more recently specimens have been found at tips derived from the Gelli and Ferndale collieries in the Rhondda Valley (I.E. Jones, unpublished data)."

None of the Mindat photos of pyrrhotite show crystals of the vivid red colour of this Coldberry micro-specimen. I'd really like to have some professional quality photos taken of the crystal. I have some queries, as pyrrhotite is a new mineral to me -

1/ Am I correct in the ID of this as pyrrhotite?

2/ It's not magnetic. Is this a rare "variety"? What's this about troilite being the non-magnetic end of the pyrrhotite series of iron abundance within the iron sulphide lattice?

3/ Have any pyrrhotite crystals been found in Teesdale before?

4/ Would this specimen be of any great interest to micro collectors and, if so, any suggestions about how I should mount it?

5/ If I upload the above (pretty crap) photos to the Mindat Coldberry page, will I get an annoying message saying that it isn't on the database for that location?

6/ If so, is this post sufficient evidence to add pyrrhotite to the location?

7/ Has anyone in Co. Durham (where I am) got the equipment to take some very high quality close up photos of this tiny crystal? For nowt?

Hoping this post has been of interest,

Regards to all,


Edited 3 time(s). Last edit at 09/17/2014 05:46PM by Uwe Kolitsch.
open | download - pyrrhotite3.jpg (27.8 KB)
open | download - pyrrhotite1.jpg (6.7 KB)
open | download - pyrrhotite2.jpg (11.8 KB)
Donald B Peck September 14, 2014 05:26PM
Hi Roger,

I don't know whether that is pyrrhotite, or not; but it is a nice crystal. If I were trying to mount it, I would mount a camel's hair brush bristle in a short piece of blackened balsa wood or cork. Then trim the hair to suitable length, select the back side of the crystal and turn it up, then touch it to drop of crazy glue and quickly the back of the crystal. The mount can then be glued into a standard plastic micro box to protect the crystal. I hasten to say, that I have never tried to mount a crystal that small. Good Luck!

steven garza September 14, 2014 05:26PM
Dear Roger;

You did a LOT of testing, have all sorts of results pointing to the fact it ISN'T pyrrhottite, & .....you STILL want it to be pyrrohottite! Why isn't i9t HEMATITE? Hematite occurs with transparency, can be BRIGHT red (when extremely thin xls), commonly has matrix-locked floaters, & OFTEN has a pseudo-hexagonal shape. Plus, it's even in an ironstone matrix. After the 1st 2 tests it wasn't pyrrohottite, you need to stop thinking in that direction; it's just making things MUCH more difficult for you, bcs you continue in the wrong direction. You are using shape, alone, for your guess; with over 4500 minerals & only a few score of shapes, it's ALMOST impossible (OK, benitoite might be that exception) for any mineral to "claim" a shape. Even when you combine S.G., hardnesses, streak, color, luster, cleagae & many other characteristics, there aren't enough of these, in any combination, to cover any mineral, exclusively.

Using your logic, ignoring your tests & going by color, why isn't that a corundum var. ruby xl? Wrong invironment? Sedimentary, right? What if the currents had dropped it there, from landmass erosion, & the concretion formed around it? It's red, transparent, is non - magnetic, & has a STRONG pseudohexagonal cross-section; it CAN be a viable candidate - however - I don't really believe that. Interestingly, I also don't believe it's hematite. I think you need to get that baby analyzed, &, I don't think it's going to be in any list of available minerals for that locality. Prehaps one of our other UK people can direct you to someone who'll help, with good equipment on hand.

Also, you might want to contact some local micromounters; they have or make appropriate mounts & boxes for their specimens & they are usually VERY helpful. Your photograph is on mark! I have a good feeling about this piece.

Your friend, Steve
Roger Curry September 14, 2014 06:07PM
Cheers for the micro-mount suggestion Don! We'll see how I get on. Steve, thanks for the interest in the specimen. I hadn't put in the post above that it's actually opaque. As you say, maybe it needs expert analysis before I can call it pyrrhotite, but there again the Wales millerite specimens have this mineral in association...

Edited 1 time(s). Last edit at 09/14/2014 06:08PM by Roger Curry.
Owen Melfyn Lewis September 17, 2014 02:15PM

I'm in Hampshire and not Co. Durham. However, I'd be happy to do some photomicrography for you up to x120, get you an SG to 2DP and, hopefully, some vague indication of RI.

FWIW, I have a small milarite of similar diminutive size and tabular hexagonal form attached to a much larger topaz (Pakistan). That milarite is orange-brown in colour but, as we know, milarite is allochromatic so colour is no indication of the species. One locality (Cumbria) reported in UK for Milarite.

PM me if you'd like the pics etc....
Alfredo Petrov September 17, 2014 04:47PM
It certainly isn't pyrrhotite, at least not now; it might have been, in the past. The crystal looks a bit porous, so I'd expect a pseudomorph. Perhaps hematite after pyrrhotite?
Roger Curry September 17, 2014 05:30PM
Thanks very much for your kind offer! I will PM you shortly and we'll sort out where I'll post it. Getting proper photos and other data is just what is needed to determine the identity of the crystal. By the way, I think we have a mix up with names. The millerite I have collected is nickel sulphide, whereas your milarite is a silicate.
Alfredo, when Owen posts pics on this thread, I'd like you to have a look. Perhaps I should have titled this thread as "Beautiful Bright Red ?Pyrrhotite? Crystal - Teesdale.
Owen Melfyn Lewis September 17, 2014 07:06PM
You are welcome, Rog, Details sent.

And, yes, I do know the difference between millerite and milarite - probably only because both are considered to be minor gemstones :-) It's just that when I looked at your pic, I thought, 'Hello, I've seen you before'. Maybe and maybe not; we shall find out in due course.

Do you have a couple of sources that give the RIs for pyrrhotite (not on the Mindat page)? Because of the small size and unpolished surface, I won't be able to get accurate RI's with a gemmo refractometer (even if within the range) but I do have a small range of immersion fluids that, by Becke's method, might let me find whereabouts, in the RI scale of things, your specimens general RI lies).

I'll try for an isogyre pattern between crossed polars too.

SG is of course no problem, given a sensitive and calibrated balance.
Ian Jones September 17, 2014 07:24PM
Hi Roger

As far as I know, there is no pyrrhotite in the south Wales coalfield. The original hexagonal platy material described as pyrrhotite was collected by Firth and described, albeit only with a visual examination, as such in his (unpublished) PhD thesis. I was always doubtful about this as much of the material I subsequently found, although notionally silvery like pyrrhotite, had a greenish surface alteration which rather suggested a nickel type mineral. We carried out XRD work at the NMW on some of my stuff and also on some of the original Firth material, which now resides at the NMW - all came up as siegenite, albeit with an unusually high iron content.. So, I am somewhat surprised to see the reference to pyrrhotite carried through to the NMW database. Different people are now involved with the on-line NMW database and clearly the earlier results have not filtered through. I'll have a word with them.

Turning to your rock, I have never seen anything like this in the south Wales coalfield, so can't really help. But I would suspect that it may once have been pyrrhotite, but is now something else. Alfredo may be right about hematite, but that's only a guess on my part.


Alfredo Petrov September 17, 2014 07:37PM
Smythite, closely related to pyrrhotite, might be another good possibility. It is highly unstable and usually exists only as inclusions inside other crystals (calcite, barite, etc), because it quickly completely oxidizes when exposed to the air. ("quickly" meaning hours or days rather than months or years)
Roger Curry September 17, 2014 10:55PM
Thanks SO much for your interest in this guys!

I'm now determined to get ID on this crystal. I'll send it to Owen tomorrow, let's see what it looks like.
Ian, brilliant you could clear up this business with the National Museum Wales' reference, as that's where I'd got the idea of the pyrrhotite ID originally.
Steve, it's looking more and more likely that your initial ID is much more credible!

Cheers lads,
Roger Curry September 18, 2014 07:22PM
Hi Guys!

This morning, my girlfriend just suggested that the tiny crystal "could be anything", meaning something man made. I hadn't considered this, and it got me thinking........ I now know what it is....

It's ****i** GLITTER! Living with my partner and her two teenage daughters, accidental glitter contamination is possible. A quick search on the internet revealed that this stuff is indeed manufactured as hexagonal flakes. You can even see the bevel I thought was a crystal face.

Apparently so much of this stuff is about (millions of kilos), it's used forensically -

Forensic Analysis on the Cutting Edge: New Methods for Trace Evidence Analysis by Robert D. Blackledge read here

It's given me a laugh, even though I'm bloody disappointed it wasn't pyrrhotite!! Thank **** I hadn't embarked on mounting the thing on a camel's hair brush bristle, or sent it to Owen and wasting his time! I hope you guys also see the funny side, and beware micro-mounters!

open | download - 201103_glitter.jpg (17.6 KB)
open | download - glitter.jpg (310 KB)
Alfredo Petrov September 18, 2014 07:57PM
No worries, Roger... We've all done that. I've wasted time trying to identify "rare minerals" under the microscope, which turned out to be lichens or insect eggs. :-(
Rock Currier September 18, 2014 08:14PM
That's really funny. If that is the worst time wasting exercise you ever engage in you will lead a charmed life and will certainly beat me by miles. I have had fun with similar things in the past. Once upon a time at the Tucson show when they had the wholesale section upstairs in a conference room one of my employees was snacking on some cracker like stuff out of a box and the stuff was fairly uniform and looked a bit like little brown worms but kind of flat. I got a flat and filled it with small cotton filled boxes and put one "worm" in each of the boxes, labeled them carbohydrates and priced them at $6 each and put them out for sale. When ever someone tried to buy one I would tell them that there was something they needed to know about the specimen before they bought it, and would then pop it in my mouth and tell them how good it tasted and invited them to do the same. We had a lot of fun with that.

Rock Currier
Crystals not pistols.

Edited 1 time(s). Last edit at 09/18/2014 08:23PM by Rock Currier.
Roger Curry September 18, 2014 08:17PM
Cheers Alfredo and Rock!

Owen Melfyn Lewis September 18, 2014 09:39PM
De nada, Rog. Saves me working out how to manipulate it for all-angle viewing when immersed :-)

Time spent on reconnaissance is seldom wasted.
Holger Hartmaier September 18, 2014 10:33PM
Hi Roger,
Glad the mystery was solved. Maybe someone in Hollywood could use this in a new CSI episode!:-)
Reinhardt van Vuuren September 19, 2014 06:36AM
I knew there was a reason I only look at crystals still attached to matrix and now I know why hahaha :D
you know what would have been even more funny, is if the glitter got lodged into the matrix when you were chipping it open, it would have been even more convincing XD.

glad you solved it and I presume had a good laugh.

I have this thing if I chip something open and inspect it under microscope and I see "something unusual" I blow it first then re-observe I'll do that several times till I'm happy that this unknown thing is actually attached and not just a nice particle. and if its laying loose and there are no traces of it on its supposed host rock well I suspect it so much I normally just ignore it and move on. But that's just me.
BTW you could always mount it as a novelty just make up a name for it like perhaps try and find the scientific name for the plastic its made of it could afford for a pretty good laugh ;)
David Baldwin September 19, 2014 08:29AM
Amazing that they make glitter so small, but apparently, it goes down to 50 microns! Yours may have come from a xmas decoration? Unusual colours always get me going. I have a goethite on calcite micro specimen with a very tiny, pink speck nestled between some calcite crystals. I estimate it to be 0.03mm across, so until I get a decent microscope, I've no hope of knowing what it is.
Travis Hetsler September 19, 2014 04:32PM

Rock Currier Wrote:
> That's really funny. If that is the worst time
> wasting exercise you ever engage in you will lead
> a charmed life and will certainly beat me by
> miles. I have had fun with similar things in the
> past. Once upon a time at the Tucson show when
> they had the wholesale section upstairs in a
> conference room one of my employees was snacking
> on some cracker like stuff out of a box and the
> stuff was fairly uniform and looked a bit like
> little brown worms but kind of flat. I got a flat
> and filled it with small cotton filled boxes and
> put one "worm" in each of the boxes, labeled them
> carbohydrates and priced them at $6 each and put
> them out for sale. When ever someone tried to buy
> one I would tell them that there was something
> they needed to know about the specimen before they
> bought it, and would then pop it in my mouth and
> tell them how good it tasted and invited them to
> do the same. We had a lot of fun with that.
Rock Currier September 19, 2014 11:02PM
I have often wondered how they make those tiny but precisely shaped pieces of copper? that are used in the making of the glass "gem" they call goldstone. Does anyone know?

Rock Currier
Crystals not pistols.
Roger Curry September 20, 2014 12:39AM
What shape are they Rock?
Rock Currier September 20, 2014 09:08PM
They appear to be tiny triangles.

Rock Currier
Crystals not pistols.
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