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Improving Mindat.orgAmazonite from Broken Hill

26th Oct 2008 07:23 UTCJohn Sobolewski Expert

Photos 20850 and 143542 claim to be Microcline variety Amazonite from Broken Hill, Australia. The book "Minerals of Broken Hill" states

the green Microclines from this locality owe their color to high lead content and calls them Plumbian Microclines which are far less common than Amazonite. Note that the description of photo 23744 is correct in explaining the cause of the green color. John S.

26th Oct 2008 08:09 UTCSteve Sorrell Expert

Recent work has indicated that these are orthoclase not microcline (Halterman, D., 2008, Fantastic Feldspar: The Plumbian Orthoclase of Broken Hill, New South Wales, Australia, Australian and New Zealand Mineral Collector Magazine No.6.).

Interestingly, Murakami et al in 2000 refer to "orthoclase (amazonite)" in the title of their article in the Journal of Mineralogy, Petrology and Economic Geology.

Regards

Steve

26th Oct 2008 08:19 UTCMark Rheinberger Expert

Hi Steve,

Do you have more information about the Australian and New Zealand Mineral Collector Magazine. Eg, who to subscribe to.

Mark.

26th Oct 2008 09:58 UTCRalph S Bottrill 🌟 Manager

I did some of the work on the Broken Hill feldspars reported in the Minerals of BH book, and the green feldspars tested range between intermediate to minimum microcline, from both XRD analysis and optics. It was previously described as orthoclase, but I have not seen the evidence to support this.

26th Oct 2008 10:19 UTCSteve Sorrell Expert

Hi Ralph. Have a look at the references in Don's article. If you want more info, I can give you his contact details.

Mark - have sent you a PM.

26th Oct 2008 11:53 UTCRalph S Bottrill 🌟 Manager

There was not much info but I know he had a reference to a Japanese Jnl which I meant to follow up

26th Oct 2008 12:37 UTCAlfredo Petrov Manager

Given that it's only the inertia of history that keeps orthoclase and microcline listed as separate species anyway, why not just call them "K-feldspar" and be done with the argument?

29th Oct 2008 17:32 UTCUwe Kolitsch Manager

Note: the colour of amazonite is caused by an elevated lead content.

I will add various references to the amazonite page (http://www.mindat.org/min-184.html).

30th Oct 2008 12:07 UTCUwe Kolitsch Manager

10 refs. added.

Mineralogists noted the connection between colour and Pb content already in the 1960s!

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