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Andrew Haighton September 26, 2011 01:16PM
I have been puzzling over a mineral which was found in the Dundas Quarry (North Section) for a while. I picked up a large rock ~80 pounds, and smashed it into smaller bits roughly 5 years ago. The rock was heavily oxidized brown and contained numerous Galena cubes, Calcite crystals, and what appears to be spherical Sphalerite crystal growths around a yellow mineral (possibly sulphur). Sphalerite is also noted on the specimen.

Then there is this mineral, which is much smaller than 1 mm, so scratching it would be impossible. It does not fluoresce under short or long wave UV, and forms tapering crystals with hexagonal cross-section. It is red to brown, and also yellow to orange. as shown in the attached photos.

I was leaning towards Wurtzite as...

1) Sphalerite and Wurtzite are of the same formula, and Sphalerite is quite common in this quarry.
2) The colour and shape are very similar to that of specimens of Wurtzite in the MINDAT gallery,
3) Some of the crystals are on the outside of the spheres have these crystals attached to the Sphalerite balls, which would be fitting with a collophorm texture (checking my textbooks from back in my geolab days), which are Sphalerite with Wurtzite and Sulphur.

In the viscinity of the mystery crystals are Galena cubes as well as Dolomite crystals.
Any thoughts would be greatly appreciated.

Andrew Haighton,
Brampton, Ontario
open | download - Image77.jpg (139.3 KB)
open | download - Image78.jpg (108.7 KB)
open | download - Image79.jpg (119.3 KB)
Alain Hanson September 26, 2011 02:30PM
Hi Andrew
I am not familiar with the occurrence, but beside wurtzite wich is a good guess, your description (red or yellow hexagons stacked in inverse pyramids) and the paragenesis could also fit greenockite
Greetings from Belgium
Andrew Haighton September 26, 2011 03:45PM
Hi Alain;

I have to admit, Greenockite was another thought I had, though, how would you determine if it was one or the other. The association with the Galena, and the fact that it in oxidized rock (dolomitic limestone hostrock, with occasional shaley zones predominantly in this quarry) lead me to believe that the crystals may be more than just Sphalerite. Oh, and the crystal form doesn't conform to anything else I have seen there.

Uwe Kolitsch September 27, 2011 05:01PM
I agree with Alain that it's most probably wurtzite.
Andrew Haighton September 27, 2011 05:18PM
Hi Uwe;

I had been puzzling over this one for a while. There was no record of Wurtzite at this quarry, but all the signs pointed that way. It's always good when your gut feeling seems to be right. That being said, I have been in contact to a collector in the states who would get it analyzed. Never hurts to be 100% sure.(tu)


Andrew Haighton November 02, 2011 02:15PM
Hi All;

The crystals have been sent in for analysis (attached). The crystals sent in were described as "Long, thin with smooth faces, but different from Sphalerite". The Fe spike is in excess of 8% I am told, though Wurtzite is up to 8%.

I am unfamiliar to this analysis, so I put it out ... What are these crystals, Wurtzite? What ever we come up with, I will set up in Mindat.


Andy Haighton,
Brampton, Ontario.
open | download - Dundas-LaFarge-Wurtzite.jpg (50 KB)
Reiner Mielke November 02, 2011 06:56PM
You cannot differentiate between Wurtzite and Sphalerite based on chemistry. The difference is structural so you would need XRD.
Andrew Haighton November 07, 2011 03:33PM
Hi Reiner;

Thanks for the input. Just need some clarification.

The Chemical Analysis indicates Sphalerite or Wurtzite, but the crystal shape is clearly not Sphalerite (6 sided and tapering). Would this then indicate Wurtzite without the XRD as Sphalerite does not do this?

If not, what else could it be?

Andy Haighton,
Brampton, Ontario
Reiner Mielke November 07, 2011 09:14PM
Wurtzite is what it would be unless there is such a thing as sphalerite pseudomorph wurtzite? Anyone know of such a thing?
Liz Fodi December 12, 2013 02:30PM
There are 3 images of specimens from this locality showing a yellowish-white material labeled 'Dolomite'. This was tested and verified by the Royal Ontario Museum as barite 8 years ago. It was tested and again verified at the ROM in the past year by Tony Steede as BARITE.
The purple colouring is definitely caused by the presence of fluorite.
Andrew Haighton December 12, 2013 02:34PM
Thanks Liz;

I will change the description.

Andrew Haighton,
Brampton, Ontario
Rob Woodside December 14, 2013 05:19PM
Thanks Liz, Baryte added.
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