John S. White

Cleavage in Quartz

Of the three, the last is perhaps the most grievous, although all are equally incomprehensible. I say most grievous because most of the major mineralogical texts have stated otherwise for many decades, and at least one for more than a century (Dana 1904). For discussions of numbers 2 and 3, see White (1999, 2000). The subject for this column was triggered by having just read a mostly scholarly book on plate tectonics in which misstatements numbers 1 and 4 were found. I have long had an amiable debate with my good friends Si and Ann Frazier, who are well-known worldwide as quartz aficionados, a term that really fails to do justice to their nearly lifelong fascination with and study of quartz in all of its forms. Just for the fun of it, I played devil’s advocate and pretended to dispute the reality of cleavage in quartz, a reality that I had long ago come to accept even though I was a skeptic at one time. After having seen numerous examples of at least one form of cleavage in quartz, this being the JOHN S. WHITE PO Box 332 Stewartstown Pennsylvania 17363 john@jwkustos.com

Hemispheroidal Fluorites From India

According to Ottens (2003), these specimens were the result of a 1998 (three years later!) discovery “in a small quarry complex 15 kilometers southeast of Nasik, east of the road to Sinnar, near Mahodari.” At that time numerous specimens began to appear on the market, most being on a matrix of quartz crystals and far superior to the one that I had sold (figs. 2 and 3). At the 1998 Munich Show, in fact, I remember seeing a quartz crystal-lined vug roughly the size of an American football that contained several large hemispheres of fluorite—a stunning piece. Virtually all of these earlier specimens were some shade of yellow or tan and were more or less transparent, especially after wetting the surfaces; the dry surface frequently masked the transparency of the For many years now the Deccan Plateau in India has been the source of quite remarkable and I thought, until more recently, nearly unique fluorite specimens. These are hemispheres, for the most part, of what are commonly transparent yellow to honey-colored fluorites. I believe that I was temporarily the owner of the first of these (fig. l), having purchased it from an Indian dealer (Nature’s Statement) at the 1995 Tucson Gem and Mineral Show for

Mineral Mysteries: Quartz Perimorphs After ?? From Morocco

35. Neither of us had any idea at the time that it was fluorite; the dealer sold it to me as gyrolite, but I knew that it most certainly was not that. After it was X-rayed by Peter Leavens at the University of Delaware, I was stunned to learn that it was fluorite. Thinking that it may well have been absolutely unique, I put what was for me a fairly substantial price on it and sold it quickly.

Mineral Mysteries: “Skunks” and Related Phenomena

For at least the past thirty years a locality in Morocco has been producing strange mineralogical objects, objects that caught my fancy the first time I saw one (fig. 1). These are commonly referred to as pseudomorphs of quartz after crystals of an undetermined mineral or minerals, but they actually are perimorphs.* Perimorphs differ from pseudomorphs because they do not replace an earlier mineral; instead they form a mineral crust, FROM MOROCCO

Mineral Mysteries: The Jacksons Crossroads Enigma, Wilkes County, Georgia

he term skunk in a mineral context first came to my attention with the photo on the cover of the March/April 1997 issue of Rocks & Minerals (fig. 1). The term was, and is, used to refer to specimens of calcite crystals upon which trails or strings of smaller crystals of amethystine quartz are preferentially aligned along three similar crystal edges, all converging at the termination of the calcite crystal. Even though I suspect that I had seen this relationship before, when I first saw the cover photo alluded to above, it seemed quite new to me, and I suspected at that time that it was quite rare. Another specimen illustrating the same relationship appears in the magazine (fig. 2); in this case the calcite crystal is a simple rhombohedron instead of a scalenohedron, and the amethyst is distributed down the centers of three rhombohedral faces. Mineral Mysteries

The Plagioclase Feldspars

T amethyst locality in Wilkes County, Georgia, known as Jacksons Crossroads has been famous since 2005 because it has produced some of the most beautiful amethyst specimens ever found anywhere in the world (fig. 1). Most notable of these are the matrix pieces that feature vibrantly colored, perfectly transparent, large amethyst crystals perched upon a contrasting white matrix composed of small and elongated, essentially colorless, quartz crystals. Most of the collecThe Jacksons Crossroads Enigma Wilkes County, Georgia

The Many Mysteries of Artichoke Quartz from China

For nearly all of my professional life the plagioclase feldspars had been divided into what have long been considered six distinct species (see table). I have always found this convention useful, even if the division was acknowledged as arbitrary. It was useful because, in general, “most anorthite occurs in contact-metamorphosed limestone; bytownite and labradorite are characteristic of igneous rocks of gabbroic composition and of anorthosites; andesine of andesites and diorites; oligoclase of monzonites and granodiorites; and albite of granite and granitic pegmatites” (Berry, Mason, and Dietrich 1983). Each of these “species” has, for the most part, a distinctly different origin. Of course, there was always the possibility of some spillover in terms of composition. Because nature had nothing to do with this categorization, natural examples of plagioclase feldspars do not always exactly fit into such convenient pigeonholes. Added to that is the fact that plagioclase crystals are often compositionally zoned, such that the cores tend to be more calcic than the last part to crystallize, which tends to be more sodic. Thus, the core may in fact be labradorite, for example, while the rest of the crystal just makes it into the andesine range. In reality, the plagioclase feldspars are simply a solid-solution series with albite being the sodium-rich end member and anorthite the calcium-rich end member. Thus, the plagioclases should have been treated, as are most other solid-solution series, with just two names, each representing the dominant composition, albite or anorthite. This fact has never been officially recognized by the International Mineralogical Association’s Commission on New Minerals and Mineral Names (CNMMN) because it has not been their role to do so with species that existed before the commission started its work in 1959. Happily, this may change because the CNMMN is now considering taking on the status of the two thousand or so minerals that predate it (E.A.J. Burke, chairman CNMMN, pers. com., 2005). These are minerals that are on what is familiarly referred to as their “GQN list,” explained below:

Let's Get it Right: The Nomenclature Debacle

and Scovil 2000), described in the caption as “Artischockenquarz,” that I was satisfied that a suitable name for the odd habit had been coined. Actually, the term artichoke quartz for a similar quartz morphology appeared earlier in Rykart (1989) and very likely has been previously used in Lapis as well. Artichoke quartz is described in Rykart as stepped quartz in which there is a mosaic development of small subindividuals adorning the main crystal either on the prism or on the rhombohedron or both, giving a rounded, vaguely artichoke-like appearance. The piece here illustrated in figure 1 represents what might be considered a classic beauty in artichoke form. That illustrated in figure 2 is also a fine example of the excellence attained by these curious specimens. Naturally, not all of the specimens from this locality are as balanced and aesthetically configured as these, but others are fascinating for different reasons. The locality for this new Chinese artichoke quartz is reported to be Shangbao (or Shang Bao) pyrite mine, Leiyang County, in the province of Hunan; however, as is the case with so many locality names in Chma, this may be presented quite differently by different dealers. (Whether due to accidental misrepresentation or just mistransliteration from the Chinese, it is common these days to encounter several variations on any contemporary mineral locality in that country. We can only hope that in time most of the ambiguities will be resolved.) As beautiful as the specimens in figures 1 and 2 are, it is that in figure 3 that is responsible for this article. This specimen is also a radiating cluster of artichoke quartz, but in this case there are cubes of pyrite scattered among the complex quartz crystals. What is truly unusual, however, is that there also is purple fluorite associated with the pyrite. The specimen measures about 10 x 9 x 8 cm and is adorned with nine larger pyrite crystals and five or so tiny ones. There are also five flat fluorite plates upon which pyrite crystals obviously once sat, but the pyrites are now missing. Without giving the quartz-

Let's Get It Right: Cavansite or Pentagonite?

T on New Minerals and Mineral Names (CNMMN) has been actively tinkering with mineral names for the last forty years or so. It has been criticized-unfairly, I believe-for officially favoring one name over another where ambiguities have existed, such as titanite over sphene, vesuvianite over idocrase, spessartine over spessartite, grossular over grossularite, and celestine over celestite; but there are very few examples where this has occurred, and, for the most part, this has not been too much of an inconvenience. However other, often more recent, changes threaten to make most introductory mineral textbooks largely obsolete because familiar common names that appear in them are no longer found in references such as Fleischer’s Glossary of Mineral Species (Mandarin

Who's Who in mineral names: Renato Pagano (b. 1938) Adriana (née Paccagnella) Pagano (b. 1939)

am sure that most of us who attend major mineral shows I such as those in Denver and Tucson are well aware that ever since the first reports of cavansite coming out of India (Wilke, Schnorrer-Kohler, and Bahle 1989; Wilson 1989), there has been a virtual flood of it in radial spheres of vivid blue, usually on pale-colored stilbite, with many dealers handling vast quantities at various times. Curiously, this sudden abundance did not appear until some twelve years after the occurrence of cavansite in India was first noted by Bill Birch, National Museum of Victoria in Australia (Wilson 1977), who actually identified it in 1974. A year earlier, in 1973, Rustam Kothavala also had found in an Indian dealer’s stock some specimens with bright blue crystals that were subsequently identified as cavansite (Kothavala 1991). “For 15 years I searched in vain,” wrote Kothavala of his attempts to locate the source of these specimens. The source turned out to be the Wagholi quarries about 20 kilometers northeast of the center of Poona (Pune), one of the quarries that he never visited. For a more detailed discussion of cavansite from India the reader is referred to Robert Cook’s Connoisseur’s Choice column in the MayIJune 1996 issue of Rocks & Minerals (Cook 1996). Cavansite was first discovered with its polymorph pentagonite in Oregon (Staples, Evans, and Lindquarries? The two species have exactly the same chemistry and form under nearly identical conditions. Well, this has happened, but with very little fanfare thus far. Pentagonite from India fEst came to my attention at the 2001 Tucson Show. An Indian dealer had some material that he claimed was pentagonite, but I was leery because it looked exactly like cavansite, so I acquired just one piece. When I quizzed him about why he thought it was pentagonite, he told me of another Indian dealer who had verified pentagonite and, in fact, even had some examples of it. So, I hustled over to that dealer, whom I knew and trusted. Upon looking at his selection I became convinced that his specimens really were pentagonite, and with great excitement I acquired a few from him as well. Once home, I was able to examine them under a microscope; it then became very clear that although those from the second dealer were pentagonite, that from the first was simply cavansite. Even though pentagonite is relatively rare with respect to cavansite, I have seen quite a lot of it subsequently, and I find that it is very easy to recognize. The typical habit for Indian cavansite, by far, is as spherical clusters of dark. rich blue color. averanY Figure I . Pentagonite crystal cluster on heulandite from the Wagholi quarries, near Poona (Pune), India. G. Edwin Maccubbin Jr. specimen, Jeff Scovil photo. ing bemeen 1 and 2 cm in diameter. They are commonly attractively scattered over a contrasting matrix