FMF - Friends of Minerals Forum, discussion and message board

[bugrock]

Can someone clarify what 'adularia' is? Mindat calls it a "variety' of orthoclase or microcline. Some apparently prefer not to use the name adularia as it is not as precise as orthoclase or microcline. Is adularia an officially recognized mineral name?

If these is a recent reference on this subject I would be interested in learning more.

I will add a few images of micro xls thought to be be adularia/microcline by several contacts. These are xls in small vugs (vugs not more than 4 mm across) found on a rock from the Nebraska copper mine, Ontonagon Co, MI this summer. There are small spheres of hematite on the surface of the xls. The Nebraska mine is very close to the Caledonia mine. It is the variety of names applied to the probable ID of these xls that brings up the nomenclature question. Some use adularia, others microcline.

Thanks,

George

[Antonio Alcaide]

[Peter Megaw]

Adularia is also very common in epithermal vein deposits...commonly massive, but alos as large pearly curved (baroque in Folkian terminology) pseudo-rhombohedral crystals to 5-6 cm across. To heap varietal name on varietal name, exceptionally well crystalized adularia from the Guanajuato District in Mexico is called "valencianite". It makes very nice specimens, especially when dusted with purple fluorite or as the matrix to fine milarite crystals

[bugrock]

Hello again,

I would like to prod the adularia discussion further as some of the mineralogical references, or so I am told, do not mention it. What is meant by 'variety', only appearance and not structure?

The term adularia is still used in the Copper Country of Michigan but apparently as common usage although microcline is the official name that applies to most crystals referred to in the region as adularia. Based on what is written under micocline, othoclase, and sanidine in Mineralogy of Michigan one needs formal analysis to verify species for this group of minerals.

In the Michigan Copper Country most minerals are of hydrothermal origin and likely microcline/adularia follows those rules.

Thanks all,

George

[Jordi Fabre]

[Jesse Fisher]

It is my understanding that the term "adularia" refers to a simple prismatic habit of orthoclase feldspar that is typically found in alpine-type hydrothermal deposits. The usage is analogous to calling the bladed form of albite typically found in granitic pegmatites "cleavelandite." The term "pericline" is also a varietal name for albite, based on a habit that is typically found in the same sort of deposits as adularia. These varietal names are based on a unique morphology, something which would not qualify as a separate mineral species in and of itself. The term "amazonite" is used for a variety of microcline that has a distinct blue or green color but is otherwise no different that other specimens of the mineral. Below is an illustration showing the difference between some feldspar varietal habits.

[Tracy]

I'm going to stir the pot a bit...

OK, so a "variety" represents a mineral that assumes different morphologies/colors. How then do you know that it's the same mineral - is it by chemical composition? If yes, then I become confused. Some of the "varieties" I've encountered are rich, in or deficient in, a particular element (e.g. skutterudite var. smaltite), thus the chemistry is different along with the morphology. Where is the point at which you draw a defining line, either by chemistry or geological origin or something I'm not thinking of, and say "all the minerals within this boundary are defined as 'varietites' of X, regardless of chemistry or morphology or energy state or...?" There's got to be some subletly I'm just not grasping here...

- Tracy

[bugrock]

Thanks Jesse,

This clarifies the issue for me and explains why 'adularia' [no matter how ingrained in usage for many specimens based on local geological conditions or habit/color or just plain usage on the part of mineral collectors] fails to be represented in some standard mineralogical texts.

Nevertheless such terms are used with such frequency that I believe mineralogists should include the terms in standard texts if only to set the record straight and inform those who might only refer to such guides in the sense of using a dictionary. The term can be included but the author then refers the reader to the recognized mineralogical names.

For instance in the most recent ed of Mineralogy of Michgian if you look up adularia
you are referred to microcline, orthoclase and sanidine because specimens called adularia from the region, if subjected to formal analysis, have been shown to fall into one of those mineralogical species. Of course the majority of specimens in existence have never been subjected to X-ray diffraction and 'adularia' is just an accepted handle. [Most 'adularia' of the Lake Superior Region is assumed to be microcline, and was deposited in low temperature veins and hydrothermal deposits of the region].

When it comes to the online resource mindat 'adularia' survives as a large entry with many specimens displayed and assume because it is a useful, if not accurate, handle to refer to many specimens. If a resource such as mindat only accepted laboratory proven material we would be denied many interesting images.


This is my take and I am not a mineralogist and would like to learn more from members of the forum, not just about 'adularia' but also about the the use of the term 'variety' in general.


George

[mmauthner]

There are no hard and fast rules as to what constitutes a mineralogical "variety": it could be coloration (via chemistry or structural quirk), enrichment with respect to an element but not such that the "impurity" is dominant in any given structural site; a difference in crystal habit...or even personal or corporate need.

Some varieties are former species names, established before the relationship to the "parent" was made more clear (e.g. amethyst...or most quartz varieties for that matter...and quartz). Many former species were reassigned to varietal status in the early 20th century.

I have been recently investigating the history of kunzite (to a ridiculous depth) and found to my surprise that the official reason for giving a new name to purple-pink-lilac spodumene is “on account of [its] unusual and characteristic phosphorescence” and nebulous "other properties". The real reason is undoubtedly to serve as a marketing tool and probably self-aggrandizement. Still happens...check out "zoltanite". The creation of many gem varieties in recent history is most certainly driven by marketing interests and has next to no scientific value.

However, the presence of varietal names on labels and in other documentation of specimens, oddly enough, does sometimes serve other purposes, mostly in determining aspects of a specimen's human history.

Cheers,
Mark

[Jesse Fisher]

I think perhaps the most obvious (and perhaps egregious) use of creating a new varietal name for marketing purposes in recent times is "tanzanite." The mineral already had a perfectly fine name, but the folks involved with marketing the new find back in the 1960s (Tiffany and Co, I believe) decided that "zoisite" didn't quite have the right sound for an expensive and desirable new gemstone. Everyone now calls purple zoisite tanzanite. Some mineral dealers even go so far as to refer to yellow or green zoisite as "yellow tanzanite" or "green tanzanite" believing this will enhance its saleability. Perhaps they're correct, but the world now has yet another poorly defined varietal name with no universally accepted definition.

[bugrock]

Names make items marketable or even highly prized. Unrelated to minerals for instance is the history of the Patagonian Toothfish. Have you ever seen that name on the menu of fine seafood establishments? But I'm sure everyone is familiar with the name given the fish by markets, Chilean Sea Bass. Look deeper into that name and you find it is not a bass and it does not always come from the waters off South America. If we insisted on gastronomic accuracy only binomial scientific names should be found on restaurant menus in which case you would order Dissostichus eleginoides.

[Jesse Fisher]

At least it doesn't have any teeth by the time it gets served up. I hate food that fights back!

[mmauthner]

Jessie,

"egregious" or "successful"? :-) ..at least they did not name it after themselves

M

[Jesse Fisher]

Touche! Marketing conquers all!

JF

[Scott LaBorde]

I am glad this question was posted. I have been wanting to see good examples of adularia. I hope to see more pictures of this mineral posted here. Thank you all for your wealth of knowledge.

Scott