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Identity HelpWilberforce Area - Black Hexagonal Crystals

10th Oct 2019 15:40 UTCDaniel Martin-Weaver

This sample was found within an old zircon mine / trench on private property in the Wilberforce area. 

This sample was measured using a Geiger counter, this one is emitting 180 counts from inside the rock and not the crystals. There are uranium mines in the area.

I'm hoping someone can point me to the right direction in IDing the crystals.


10th Oct 2019 15:52 UTCRichard Gibson

Looks reminiscent of fluoro-richterite to me. 

10th Oct 2019 16:02 UTCAndrew Debnam

Hello Daniel, please take a read of 

It is hard to see any cleavage in the photo so I am assuming an Amphibole of some kind at this point

10th Oct 2019 18:21 UTCDaniel Martin-Weaver

Thanks for the responses so far folks, much appreciated.

Sorry for the trash photos, I'll get some better ones. The well formed crystals are hexagonal in shape, likely fractal. 

I found a larger, somewhat intact crystal, nearly 2 inches in diameter, obtained from the same location.

I'll likely visit the ROM to get obtain the ID, which I have never done before.

10th Oct 2019 19:06 UTCPaul Brandes Manager

Welcome to Mindat, Daniel!

I would agree with Andrew in that it is one of the amphibole minerals from the area. However, you will not be able to determine which one simply by visual observation.

11th Oct 2019 01:01 UTCDaniel Martin-Weaver

 Thanks for the warm welcome Paul. Appreciate this website and all of its crowd sourced data!

10th Oct 2019 20:52 UTCErik Vercammen Expert

This is not an amphibole but a pyroxene diopside - enstatite....) The angles between the faces are (around) 90° or 135° (90 + 45°) and that is a pyroxene; for an amphibole, the angles are around 120°.

10th Oct 2019 21:06 UTCSusan Robinson

I think it is most likely diopside or augite, since the crystals show typical monoclinic symmetry of these species.   The majority of pyroxene, such as those in the Bancroft - Wilberforce area are typically in the diopside-hedenbergite-augite series.   

Amphiboles appear more splintery with perfect 56 - 124 degree cleavage.   The pyroxenes (diopside, etc.) typically show cleavage closer to 90 degrees.   One word of caution when measureing cleavage angles of the pyroxenes: be sure you are looking at two cleavage faces and not parting planes.  

George Robinson

11th Oct 2019 01:20 UTCDaniel Martin-Weaver

Hi Eric,

Thank you for the suggestion. 

I measured the angles at 135 degrees for the hexagonal crystals in both pictures.

10th Oct 2019 21:34 UTCFrank K. Mazdab Manager

I also suspect that these are diopside.  In the top photo, one crystal catching the light in the middle upper right of the specimen even appears to show most of the edges of  a classic "stop sign" pyroxene cross-section.  But differentiating amphibole from pyroxene can be admittedly tough to ascertain from just a photo, so as others here have recommended, look for a damaged crystal, rotate it to allow different cleavage surfaces to catch the light, and best estimate whether the required rotation is closer to ~60/~120 (amphibole) or closer to ~90/~90 (pyroxene).

10th Oct 2019 21:47 UTCAndrew Debnam

Daniel if take a look to see if you can find a broken crystal that will help. The pyroxene often exhibits distinctive parting. The broken crystal at right angles to its long axis will have quite a flat face similar to the Fluorapatite  when it is broken. I am sure a can find a broken Diopside and post a picture. As a side note being momoclinic does not differentiate  amphibole from pyroxene. 

10th Oct 2019 21:55 UTCPaul Brandes Manager

Hmm that was odd. When I posted earlier, Daniel's second post was there, but the photo was not showing up (dead link). Now that it is, I see the angles and yes, it looks more like a pyroxene.

10th Oct 2019 23:31 UTCAndrew Debnam

Yes Paul, I only saw one image originally as well. Perhaps I should not being this on my old cell phone anyway. Here is a picture of a parted Diopside my son sent me from home. Not sure if can seen but the parting has a smooth sheared face. As pointed out the Amphiboles have splinters . Looking now at both pics on my laptop yes more than likely a pyroxene. 

11th Oct 2019 01:25 UTCDaniel Martin-Weaver

Here's a higher resolution  picture of the large rock.

11th Oct 2019 01:35 UTCDaniel Martin-Weaver

Side note: according to a Geiger counter, this one is emitting 180 counts. Not from any of the crystals, but likely from the inner contents of the rock.

Is this something worth exploring further?

11th Oct 2019 01:27 UTCDaniel Martin-Weaver

Smash time.

Here's the before picture of a lower grade specimen.

11th Oct 2019 01:30 UTCDaniel Martin-Weaver

Here's the before picture of a lower grade specimen.

Before picture, from the backside.

11th Oct 2019 01:30 UTCDaniel Martin-Weaver

Here's the after picture of the lower grade specimen. 

It does not appear to break along any cleavage planes.
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