CONNELITE: ANOTHER RARE BLUE COPPER MINERAL

This year in Tucson I was able to pick up a specimen of connellite on cuprite, something that I have been after for a couple of years.  I am fascinated by the numerous blue specimens associated with copper, mostly as oxidation products.  Azurite is probably the best known blue copper mineral; however, there are a host of others.  I have been trying, slowly, to document some of these minerals in my small collection by offering postings on this blog.  So, the search for connellite.  And, in keeping with my theme at 2015 Tucson (see the previous postings on Show Reports] I was searching for specimens under the price of a measly five bucks.

Massive cuprite with two areas of fibrous blue connellite.  Width of specimen 2 cm.  Collected Bisbee, Warren District, Cochise County, Arizona.

Cheap---probably---but I like to think frugal!  Much more frugal than Bob Jones in his Rock and Gem articles (later a book).  I purchase minerals, not for an office display nor a case at the local rock show, but to learn as much as possible about the species and then “write it up” for this blog or a club newsletter.  One of my goals in life is to continue, “till the end,” to be a life-long learner.  So, spending something in four figures would put a crimp on purchasing 200 other specimens---my learning curve would bottom out.  Strange---perhaps, but this life–long learning is a passion and helps keep me intellectually alive.  As I am fond of saying, life is good.

                   In the end, it is not the years in your life that counts,

                             It’s the life in your years.        A. Lincoln. 

Connellite is a pretty rare mineral, or at least a very uncommon hydrous copper chloro-sulfate.  MinDat lists 278 different localities for the occurrence of connellite; however, there seems to be only a few places where the rockhound might have a chance of locating a specimen (assuming you could get on the property).  In 1995 Anthony and others wrote “One fist-sized specimen from Bisbee probably contains half of the connellite known in the world.”  

This rare secondary mineral [Cu₁₉(SO₄)(OH)₃₂Cl₄-3H₂O] is found  in the oxidized zones of copper deposits with Bisbee being a prime example of its occurrence.  It has a deep blue to royal blue color, a vitreous luster, a hardness of 3 (Mohs), and occurs as beautiful tiny blue tufts to flattened fibrous layers.  These small crystals are mostly translucent.  Its most common associated mineral is cuprite but also other secondary copper minerals such as azurite, brochantite, caledonite and malachite.  Any observed fracture is splintery. 

Photomicrographs of fibrous connellite on cuprite.  Width of patch ~4 mm.

Photomicrograph of fibrous connellite on cuprite.  Width of patch ~3 mm.

There is a solid solution between connellite and a very rare nitrate termed buttgenbachite [Cu₁₉(NO₃)₂(OH)₃₂Cl₄-2H₂O],  It would be very difficult for me to distinguish between the two minerals based on observable physical properties.  For an in-depth discussion of this solid solution series see Hibbs and others (2006).

REFERENCES CITED

Anthony, J.W., S.A. Williams, R.A. Bideaux, R.W. Grant, 1995, Mineralogy of Arizona (Third Edition): The University of Arizona Press, Tucson.

Hibbs, D.E., P. Leverett and A. Williams, 2006, Connellite from Bisbee, Arizona:  A single-crystal x-ray study: Axis, v. 2. No. 2.

BABINGTONITE: MA STATE MINERAL

I was rummaging around some web sites the other day and reading about various minerals that some states had designated as their official “State Mineral.”  Most were quite familiar such as rhodochrosite (Colorado), gold (Alaska) and copper (Arizona) among others.  However, one particular mineral that caught my eye was babingtonite, the official mineral of Massachusetts.  I searched the back recesses of my mind and sort of remembered that it was a dark colored mineral, a calcium iron magnesium silicate somehow associated with zeolites.  I also knew that a small specimen was somewhere in my collection---so I dug it out; however, it was not from Massachusetts but was collected at the Iron Cap Mine in Arizona.  I also then made a decision to hunt for a New England specimen during my February travel to the Tucson Shows.

I enjoy hunting for unique minerals in all sorts of small mineral venues and in dusty trays and so was rewarded in Tucson with a nice glittery Massachusetts specimen with hundreds of small babingtonite crystals.  Another serendipitous moment!

Babingtonite [Ca₂(Fe,Mn)FeSi₅O₁₄(OH)] crystals have a very dark green to black color and a vitreous luster.  It is fairly hard at 5.5-6.0 (Mohs) and has stubby to prismatic and striated crystals.  They are opaque and actually quite impressive.  They also are difficult to photograph, at least to me.

Babingtonite is in a solid solution series with manganbabingtonite where some of the iron is replaced with manganese [Ca₂(Mn,Fe)FeSi₅O₁₄(OH)].  It is probably impossible for me to tell the difference between the two minerals.

Although babingtonite sometimes occurs in low temperature hydrothermal veins found in granite pegmatites, it is most common in mafic volcanic basalt where it is found in vugs and often associated with various zeolite minerals, quartz, calcite and prehnite. 

Tiny black crystals of babingtonite on a matrix.  Length of specimen ~4 cm.  The crystal faces reflect light.  Specimen collected from Blueberry Hill Quarry, Massachusetts.

Parts of Massachusetts have several bedrock quarries where “trap rock” is quarried for dimension stone or road aggregate.  Trap rock is just a common name that refers to extrusive volcanic rocks such as basalt or a fine grained intrusive rock commonly found in sills and dikes (diabase).  In fact, much of New England displays erosion-resistant ridges representing Triassic intrusive or extrusive rocks trending across the countryside.  Many of the ridge quarries contain rocks with vugs of all sizes.  These openings in turn contain a wide suite of zeolite minerals along with other minerals such as prehnite and babingtonite and are a collecting source for New England rockhounds.  These basalts and diabases are associated with the breakup of supercontinent Pangaea into the proto-continents North America and Europe.  As Pangaea split, a series of valleys formed, basalt squeezed out, and intrusive sills and dikes formed.  

Photomicrograph of section of specimen above.  The individual crystals are 1 mm. and smaller.  These tiny black crystals are difficult to photograph.

My purchased specimen came from the Blueberry Mountain Quarry near Woburn, Massachusetts where MinDat lists 32 valid minerals. Beside the nice crystals of babingtonite, the specimen contains extremely small strands of “byssolite,”something not listed by MinDat as being present.  “Byssolite” is not a valid mineral but a variety of the Amphibole Supergroup and may be hair-like fibers of several minerals.

Small strands of “byssolite” with the largest ~ 1mm in length.  Same specimen as above.

The initial specimen of babingtonite in my collection, acquired several years ago, came from the Iron Cap Mine, Landsman Camp, Aravaipa District, Graham County, Arizona. I later found out that the identification was incorrect and the crystals were manganbabingtonite.  Of course I cannot extinguish between the two minerals based on external physical characteristics!

Crystals of manganbabingtonite with acicular crystals of johannsenite.  Collected at Iron Cap Mine.  Length of left largest crystal ~3 mm.

Individual crystal of manganbabingtonite from the Iron Camp Mine.  Length about 2.5 mm.

Another mineral of interest in the specimen is johannsenite, a somewhat uncommon calcium manganese silicate [CaMnSi₂O₆], sometimes containing iron, which is the dominant pyroxene at the Iron Cap Mine (Anthony, 1995). The physical properties of johannsenite vary: color ranges from brown to black to gray to green to light blue to yellow to violet and others; it is translucent to transparent; the habit is massive to acicular needles to radiating aggregates to splintery; the luster varies from greasy to vitreous and the hardness is 6 (Mohs) although the acicular needle masses break apart easily. It forms in contact metamorphic zones—as does the babingtonite. Johannsenite in my specimen is composed of massive green prismatic crystals or cleavage fragments (angles of 87⁰ and 93⁰ typical of pyroxenes).

A second specimen of johannsenite from the Iron Cap has very dark green patches of acicular crystals.

Johannsenite is in solid solution with hedenbergite when the iron completely replaces the manganese [CaFeSi₂O₆] and with diopside as magnesium replaces the manganese [CaMgSi2O6].  In a process that somewhat confuses me as to process, johannsenite alters to pink rhodonite (see Livi and Verblen, 1992, for a detailed report on this process.)

Green patchy acicular crystals of green johannsenite (J) with cream-colored masses of tiny acicular crystals of something, perhaps ??nekoite (?)[Ca₃Si₆O₁₅-7H₂O] and metallic galena (G).

The Iron Cap Mine is a former surface and underground Pb-Zn-Ag-Cu-Au-Fluorspar mine where the major ores were sphalerite (zinc) and galena (lead).  Mineralization is found in vein deposits hosted in the Horquilla Formation (Pennsylvanian) and the Pinkard Formation (Cretaceous). Some ore veins occur in faults between formations while others are found wholly in the limestone beds. The mine area also includes numerous intrusive veins of Cretaceous and Tertiary age cutting across Paleozoic rocks (Simons, 1964).

Anthony and others (1995) noted the Landsman claims contain manganbabingtonite in veins containing sphalerite and galena in a contact metamorphic zone developed in limestone and shale.  Therefore, the occurrence is different than the Massachusetts basalt vugs.

I've always loved life, I've never known what's ahead.  I love not knowing what might be round the corner.  I love serendipity.

                                 Twiggy

REFERENCES CITED

Anthony, J.W., S.A. Williams, R.A. Bideaux, R.W. Grant, 1995, Mineralogy of Arizona (Third Edition): The University of Arizona Press, Tucson.

Livi, K.J.T. and D.R. Veblen, 1992, An analytical electron microscopy study of pyroxene-to-pyroxenoid reactions: American Mineralogist, Volume 77.

Simons, F.S., 1964, Geology of the Klondyke Quadrangle, Graham and Pinal Counties, Arizona: United States Geological Survey Professional Paper 461.