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Augite

Posted by Rock Currier  
avatar Augite
May 27, 2009 10:02AM
©


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Click here to view Best Minerals A and here for Best Minerals A to Z and here for Fast Navigation of completed Best Minerals articles.


Can you help make this a better article? What good localities have we missed? Can you supply pictures of better specimens than those we show here? Can you give us more and better information about the specimens from these localities? Can you supply better geological or historical information on these localities?

Below are some preliminary notes I have made about Augite. This entry and thread has been made as a place holder for information that you will hopefully contribute about Augite. It should be in no way be thought of as a claim I have staked out to write about this mineral, and in fact is an invitation for someone to step forward and create the article about this mineral. If you are so inclined and have questions about the format that such an article should have, go the The welcome topic at the top of the Best Minerals forum and read what has been posted there. Also take a look at some of the more mature articles that have already been written like Rhodochrosite, Adamite, Millerite etc. You will need also to pick out other images of Augite that will go into the article.



Augite
(Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6] Monoclinic
Augite xl on orange Calcite, Yates Mine, Otter Lake, Québec, Canada 28mm wide© 2001 John H. Betts


Quote
Augite is just a dirty diopside, so it will eventually suffer the same fate as andesine and labradorite and be demoted to varietal status.
Alfredo Petrov 2009



Augite Display collections?
(Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6
When localities are described in mineralogical literature it is common to see an alphabetical list of minerals found at the locality. Many times the lists will contain only the general name pyroxene. Which of the more than 20 various pyroxene group minerals might be found at the locality is up to the imagination of the reader or the subject for further study by researchers. Augite is a common mineral in the pyroxene group. Sometimes augite will be described but only as part of the diopside-augite series which also includes hedenbergite. Augite is fairly common but good specimens are rare though not expensive when encountered in dealers stocks. That is because they are black and not very attractive. Most of the ones you do see are not very shiny, dull black and not well formed. Augites are commonly are found in eruptive rocks. I have also wondered over the years just how accurate the identifications were of the specimens that were labeled augite. An accurate chemical analysis must be done as it is impossible to sight identify the species. Recently mineralogists have been screwing around with the nomenclature of pyroxenes and amphiboles and I think that most museum curators and collectors don’t have a clue what their augites and related minerals really are.
I don’t think I have ever known of or heard about a collector who collected augites and you hardly ever see them in display cases. At any rate, below are a few images of some augite specimens I have encountered over the years.

Augite
Antarctic
South Victoria Land, Ross Island. Little black one inch crystals from a place you would definitely not want to live.

Augite
Australia
Victoria, Cape Grant, Portland Harbor Trust Quarry. The augites from this locality are up to 6.5 cm long and are associated with andesine crystals up to 3 cm long and ilmenites to about 1.5cm in diameter. Typically the augite and andesine are around the 1 cm size. “The augites are generally sharp, prismatic and very glossy black. Some have hollow terminations. The ilmenite forms lustrous black plates. Specimens generally consist of a mixture of the three main minerals with andesine the most abundant. The largest specimen I have seen is around 60 cm across…part of a thin vein…atop a slab of the fine-grained basalt. Some of the minerals are coated in clay which can be removed with a quick and careful dip in hydrofluoric acid. …The minerals occurred in fissures and vugs in the basalt. Basically the rock is like a pegmatoidal basalt with an assemblage of high temperature minerals, diopsidic augite, andesine and ilmenite with a lower temperature suite consisting of chabazite, phillipsite and calcite.(growing on the andesine and augite) …The chabazite is 3-4 mm across and is phacolitic. The phillipsites are about the 2 mm size. The calcite is typically golden brown, scalenohedral, up to 1 cm with some spherical aggregates up to 1.5 cm across. The majority of the material was collected in the late 1970s and early 1980s and the quarry no longer operates. …the rock is like a pegmatoidal basalt with an assemblage of high temperature minerals, ”1
1 Personal communication 2002, Dermot Henry, Senior Collection Manager, Geosciences, Melbourne, Victoria, Australia.

Augite
Brazil
Sao Paulo, Iguape River Valley, Jacupiranga Mine. This phosphate mine is about 230 km southwest of São Paulo. “Augite is the most common constituent of the vugs, occurring as sharp, dark green crystals measuring up to 3 cm, commonly associated with fluorapatite and phlogopite crystals.1 I have never seen a good one and the author of the article in the Mineralogical Record did not choose to include a picture of one in his article.
1 Mineralogical Record, Vol. 15, 1984, p267.

Augite
Canada
Ontario, Lake Clear-Kuehl Lake. “Pyroxene is a common mineral at calcite dike contacts. EDS analysis indicated that pyroxene is a sodium-bearing augite (less than 1 weight percent Na). Crystals are generally short prisms and dark green to black in color with a rather dull luster probably due to surface alteration to amphibole. Individual crystals, while seldom exceeding 15 cm in length, can form large groups weighing up to 50 kg. This is particularly true at the Smart mine where augite is associated with large microcline-perthite crystals.1 These are pretty ugly creatures and not of much interest to collectors or even to museums for display purposes. Sometimes these kinds of specimens will be included for educational purposes. They will certainly not attract a big crowd of spectators the way a room full of gem stones will.
1 Mineralogical Record, Vol. 13, 1982, p212-3.

Augite
Ontario, Grenville Province. The Grenville Province is a rock formation that is part of the greater Canadian Shield formation and is composed mostly of metamorphic and igneous rocks. Over the years it has produced many interesting mineral specimens. “Like the amphiboles, clinopyroxenes occur abundantly in the Grenville. Also, like the amphiboles, chemical variation is the determining factor in the proper nomenclature. All too often anything that is green becomes labeled “diopside,” and anything black, “augite.” Although this method may work some of the time, it precludes a positive identification. Because of widespread occurrence, only the more important localities can be considered here.”1 It is difficult to find an attractive augite specimen from this region.
1 Mineralogical Record, Vol. 13, 1982, p78.

Augite
Czech Republic
Bohemia, Paskapole. Augite specimens “…sharp, dull black to blackish green, perfect crystals…a few of these were still in the matrix of fine-grained volcanic rock in which they occur as phenocrysts, but most were floaters, both singles and twins, in textbook monoclinic forms, ranging up to 5 cm long. Three or four dealers had these; some specimens were dated 1989, and none cost more than about $8.”1 The above were specimen described at the Prague gem and mineral show in 1991.
1 Mineralogical Record, Vol. 22, 1991, p459.

Augite
Italy
Mt. Vesuvius. “Sharp lustrous black augite crystals, usually doubly-terminated and commonly to 1” in size, occur on Mount Vesuvius, near Naples…”1
1 Mineralogy for Amateurs, Sinkankas, p493.

Augite
Mexico
Oaxaca, Ayoquesca, La Panchita. The augite specimen shown here is in the Romero collection at the University of Arizona at Tucson. It looks nice, but quantities of these specimens would be difficult to sell.

Augite
United States
New Mexico, Winston, Willow Creek. “The host rock is a porphyritic rhyolite…Augite is not abundant but appears as very fine, transparent, burnt-orange prisms, some of which are almost hairlike. Titanite having the same burnt-orange color as the augite is quite common; the wedge-shaped crystal habit allows easy identification.”1
1 Mineralogical Record, Vol. 20, 1989, p60.

Augite
New York, Diana A & B. The A specimen from New York is the best looking of the two with its shiny black crystals. The other is ugly as sin but was kept, I suppose, because it is from a venerable old collection.

Augite
Pennsylvania, Chester County, St. Peters, French Creek Mine. “Dark green augite generally is massive. Eyerman (1889) reported perfect crystals to 4.2 cm. Chamberlin (1887) described deep olive-green drusy crystals grouped into stalactitic forms. Augite is associated with hornblende and is a common accessory in the diabase.”1
1 Mineralogical Record, Vol. 25, 1994, p113.



Click here to view Best Minerals A and here for Best Minerals A to Z and here for Fast Navigation of completed Best Minerals articles.

Rock Currier
Crystals not pistols.



Edited 3 time(s). Last edit at 12/27/2012 07:55AM by Rock Currier.
avatar Re: Augite
May 27, 2009 10:53AM
    
Hi Rock, here is an augite twinned crystal from Mt. Vesuvius

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Re: Augite
May 27, 2009 03:02PM
Augite is just a dirty diopside, so it will eventually suffer the same fate as andesine and labradorite and be demoted to varietal status.
avatar Re: Augite
May 27, 2009 07:44PM
Can I quote you? What am I talking about! I did quote you.

Rock Currier
Crystals not pistols.
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