Monday, May 5, 2014

CALLAGHANITE; A RARE BLUE CARBONATE




BESIDES BLUE MINERALS ARIZONA HAS SOME FANTASTIC SUNSETS SUCH AS THIS PHOTO NEAR CAVE CREEK.


I have noted before in these postings (especially see August 21, 2012) about my first trip, in 1967, to Salt Lake City, Utah, so that I could attend graduate school.  I was just a small town Kansas kid and came from a high school of 48 students (that is total for all four grades)!  If I misbehaved in school it was likely that my father knew about it before I reached home after the end of classes.  Word seemed to travel rapidly in a small town. The great “things” about this childhood included participating in a variety of sports, getting a pretty fair education (four years of math, science, and English) and being able to spend any free time tromping around the countryside collecting rocks, fishing, camping, and hunting for a mythical cave (see posting July 23, 13). 

I attended the University of South Dakota and completed a MS degree and now was heading west (with a spouse of 5 days) to experience life as a frontiersman (or so I dreamed) and get another degree.  But, upon popping over the Wasatch Mountains and seeing Salt Lake City I was flat-out scared.  Wow, this was a big city (~250 ka) and the University was probably really large (everything is relative to the times).  We had little money but found a small apartment where the rent was $35 every two weeks, and we were off.

At that time the University of Utah followed an “old school” model with  three different and separate departments:  Geology, Geophysics, and Mineralogy; each area had a chair and faculty.  All departments had good faculty members; however, I became quite fond of two in geology—Armand Eardley, a well-respected structural geologist and stratigrapher Lee Stokes (my major adviser).
  
The Utah Geological Survey was intimately associated with the departments and their Associate Director was an economic geologist by the name of Eugene Callaghan.  In 1968 the three departments consolidated into the Department of Geology and Geophysics and Callaghan became the Chair.  In retrospect, I suppose securing an external chair was an appropriate political move that would not “favor” a single department.  At any rate, I was spellbound when listening to Callaghan talk about his past careers and travel spanning most of the world’s continents, especially his stint as chief geologist for Cyprus Mines Corporation, and his field work in 1930’s Nevada. They were fascinating stories.

Over the years since leaving Utah in 1970, I had not really thought much about Dr. Callaghan except when I read an article detailing some of the interesting geology of Cyprus.  Not being a mineralogist, I often had difficulty understanding the complex ore mineralization present on that island! 

This winter, while rummaging through some mineral specimens at a small venue at the Tucson shows, I came across a thumbnail specimen with a smear or two of blue color.  Now, I am a sucker for blue minerals so shelled out a couple of dollars and tucked it away.  Imagine my surprise when I returned home and checked out the “blue specimen” labeled Callaghanite from Nye, County Nevada, and found that the mineral was named after the former department chair at the University of Utah--one of those serendipitous moments. 
 

PHOTOMICROGRAPH OF A CALLAGHANITE VEINLET WITH TINY NODULES OF WHITE DYPINGSITE [Mg5(CO3)4(OH)2-5H2O] or HYDROMAGNESITE  [Mg5(CO3)4(OH)2-5H2O.  THE NODULES ARE LESS THAN 1 MM IN WIDTH.


MAGNESITE OR HYDROMAGNESITE (MATRIX) WITH A BLUE INCRUSTATION OF CALLAGHANITE.  WIDTH OF SPECIMEN  ~2.7 CM.

Callaghanite was named by Beck and Burns (1954) and was described as “…small, azure-blue crystals from the working pits of the Gabbs Refractories Inc. Gabbs, Nevada [Nye County] and is…a hydrated basic copper, magnesium, calcium carbonate, Cu4Mg4Ca(OH)14(CO3)2-2H2O [now noted as Cu2Mg2(CO3(OH)6-2H2O]…The mineral occurs near peridotite dikes intrusive into magnesite and dolomite…part of the Luning formation of Upper Triassic age...At the contact between magnesite and diorite, magnesite has been changed to brucite and diorite has become more basic by assimilation of magnesia. Apophyses of diorite within brucite may be changed completely to serpentine. A thin band of forsterite often marks the boundary between the serpentine and brucite…[Callaghanite] generally is found within this serpentine-forsterite-brucite zone where it occurs as tiny disseminated crystals, as encrustations, and as veinlets. The field relationship of the mineral suggests that it is hydrothermal in origin.”  Beck and Burns  also suggested that the hydrothermal solutions normally would have precipitated azurite but because of the magnesium and calcium in the surrounding rocks, Callaghanite was formed.

Callaghanite is usually reported as being “very rare” and for decades was only known from the type locality.  Beginning in 1988 reports begin to trickle in about rare occurrences in Austria, Germany, Italy, and Oklahoma, USA.  See Mindat.org for references. 

The Deseret News of Salt Lake City, reporting on the death of Dr. Callaghan, reported: his distinguished professional career spanned 62 years and seven continents. He received his B.A. and M.A. in geology from the University of Oregon and a Ph.D. in geology from Columbia University in 1931. From 1928-46, he conducted research and geologic mapping in Utah, Nevada, Massachusetts, Puerto Rico, and South America for the United States Geological Survey. In 1946, he was appointed professor of economic geology at Indiana University.  During 1949-57, Dr. Callaghan directed the New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico. After 1957, he served as international consultant to Haile Mines Corp., DeLiew, Cather & Co., and other firms for which he conducted surveys in Cuba, Mexico, Canada, Turkey, Iran and other countries. From 1958-60, he was chief geologist for Cyprus Mines Corp., conducting studies in Cyprus, Greece, Israel, Arabia, Spain, Portugal and Morocco.  During his retirement (post 1972), Dr. Callaghan continued geologic consulting and attending professional conferences in Ireland, Scotland, Kenya, People's Republic of China, Australia, and Antarctica, among others.

As a summary note, Callaghanite actually was named for Dr. Callaghan’s time as Director of the New Mexico Geological Survey and his work with magnesite.

REFERENCES CITED
Beck, C.W. and J.H. Burns, 1954, Callaghanite, a New Mineral: American Mineralogist, v. 39.

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