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Cu-Austinite vs Conichalcite from Ojuela

Posted by Peter Hargis  
Peter Hargis April 27, 2012 05:02PM
Looking through the various photos uploaded for the Ojuela Mine, I'm noticing that gemmy Cu-Austinite and gemmy Conichalcite look very similar (and even the Arsenodescloizite and Cu-Adamite can look similar). One of the differences I notice is that the gemmy Conichalcite comes in small distinct xtals more often than the Cu-Austinite (more of a mass of xtals). Does anyone know of a good "eyeball" test to tell the difference between the two?

For instance, these two look similar to me...

"Always do right. This will gratify some people, and astonish the rest." - Mark Twain
Richard Gunter April 27, 2012 05:45PM
Hi Peter:

I did a B.Sc. thesis in 1977 on the Ojuela Mine Conichalcite-Austinite Series and found that there is no visual method of determining the difference between phases. I also found that it is a three component system with significant Pb in some of the crystals. The Pb altered the unit cell dimesions sufficiently that even XRD was not always accurate. The sample posted on my page has XRD cell size and microprobe data so I know what that sample is. The thesis was completed before the characterization of Arsendescloizite but I did not find any samples that were rich enough in Pb to qualify as a new phase.
Peter Hargis April 27, 2012 06:04PM
Interesting... So I wonder if it would be more accurate to list a mineral as being from the series instead of a particular member of the series?

Have you thought about adding your research to the mineral page for the series, as a reference?

"Always do right. This will gratify some people, and astonish the rest." - Mark Twain
Richard Gunter April 27, 2012 06:24PM
Hi Peter:

Unless the samples are colourless, in which case they are probably Austinite, all of the Conichalcite-Austinite samples are members of the series. I never thought of putting the cell's size and microprobe analyses with the posted sample but I will do that to assist others.
Richard Gunter April 27, 2012 06:44PM
Hi Peter:

I have added the cell size and microprobe results to the note on photo #428254. I hope this helps clear up the confusion a little bit.
Peter Hargis April 27, 2012 07:17PM
I appreciate the help!

"Always do right. This will gratify some people, and astonish the rest." - Mark Twain
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