Pictured above left and right are overviews of Glenn Archer's Australian Outback Mining tent at the Arizona Mineral and Fossil Show's Mineral and Fossil Marketplace location. The Mineral and Fossil Marketplace is a tent show located between the Executive Inn and Vagabond Plaza Hotel shows. Australian Outback Mining has become a regular stop of mine at the Tucson Show for ogling and acquiring Australian rough for carving and cabbing, as well as display specimens of interesting rocks. Unlike most dealers who are in the middle between the miners and the collectors, Glenn is a working miner and direct source for the rough he shows. As a result he is very knowledgeable regarding the material he offers and their localities which is something I have come to appreciate in a dealer, not to mention his pricing, which reflects the direct source.
Glenn and his lady friend Margy are pictured at left. Glenn and Margy also attend and sell at the Quartzsite show prior to coming Tucson. While they obviously enjoy themselves at Tucson, I imagine they are no doubt pretty ready to get back down under by the end of the Tucson Show. Glenn's enthusiasm for rocks and his work is evident and he is at the ready to field questions regarding his offerings and Australian mining and geology in general. Glenn has also begun work on a web site where he presents information on the rocks he mines and sells, so be sure and also visit www.outbackmining.com for further and future information and reference on the materials shown below.
Right off the bat I was drawn to a barrel top covered with sliced and polished specimens of a conglomerate from Field's Mine in Western Australia. The price spread on these ran from about $9 to $35 depending on the size. This is a unique and pretty material to my eye and I didn't have to consider the piece shown in hand at right before it decided to come home with me. This one weighed a little over 2 pounds and was priced at $15. It is about 1 5/8" thick and will yield about half a dozen very nice slabs. I was looking at this material through the eyes of a cutter when I was at Glenn's tent, but after having a little more time to appreciate this rock I've decided if I am going to cut this one I also need to go back and obtain another chunk to preserve as a geological display specimen.
I think conglomerates are interesting due to the geological stories they tell and this material provides a textbook example in hand of a conglomerate. Conglomerates are of course conglomerations of once freely moving pebbles on the surface of the Earth which were buried at some point in time and subsequently cemented together and consolidated as sedimentary rock. Some conglomerates are transported by geologic processes to depths where the pressure and heat are sufficient undergo various degrees of metamorphism.
Most conglomerates contain a good deal of sand as both the matrix in which the pebbles are embedded and as associated beds and lenses of sandstone. The pebbles in most conglomerates are rounded and smoothed through transportation as they are tumbled along by vigorous streams and rivers. Thus the sources of the eroded material forming a conglomerate can be located a significant distance from the deposit. It is possible to trace the pebbles in a conglomerate back to their source and few other rocks contain so complete and specific record of their source and history. The special value of conglomerates to the process of geological detective work is the pebbles are more complex and have more character than finer sediments. The more a sediment is broken down into its constituent mineral grains the more it looks like other sediments.
Depicted above are two billion year old Australian stromatolite specimens. These specimens contain a thin layer of conglomerate with reddish pebbles underlying the laminated stromatolite structures, which are a perfect accent and attractive to my eye.
Stromatolites are the oldest known fossils recording life on Earth, with some dating back more than 3 billion years. Stromatolite fossils are micro-laminated sedimentary structures, the by-products of life processes of colonial organisms known as cyanobacteria and other microbes. Cyanobacteria derive their name from the pigments phycocyanin and allophycocyanin, which give many of them a characteristic blue green color. Cyanobacteria are photosynthetic prokaryotes, which are primitive organisms making their living with cellular chemistries similar to plants, but lacking the DNA-packaging cellular nucleus characterizing all eukaryotes - single and multicellular plants and animals. Stromatolites thrived in the early seas, with stromatolite populating species building reefs resembling those built by modern day corals.
Photosynthesizing cyanobacteria were responsible for the creation of Earth's oxygen atmosphere during the Archaean and Proterozoic Eras, and in doing so these relatively primitive organisms played a tremendously important role in shaping the course of succeeding evolution and ecological change throughout Earth's history. The oceans and atmosphere had a very different chemistry lacking free oxygen, unsuitable for life as we know it today, prior to the appearance and activity of cyanobacteria. They were the dominant lifeform on Earth for over 2 billion years and the builders of Earth's first reefs.
These specimens are from the Irregully Formation in the western part of the Bangemall Basin, near the Ashburton River, not far from Kooline Station. They occur in an extensive outcrop of dolomite where the recorded stromatolite forms include Conophyton garganicum australe and Baicalia capricomia as well as undescribed forms. The Bangemall Basin is a Middle Proterozoic sedimentary basin with an age of about 1100 million years. Like most of the other materials on Glenn's tables, these specimens have cut and finely polished faces, which makes them very attractive as specimens. Cutting and polishing faces on his rocks is doubt worth Glenn's time and effort in terms of enhancing their appeal and marketability. However, Glenn almost does too good a job of this regards the eye of a camera, as the reflections and glare on these highly polished surfaces can make capturing serviceable images of Glenn's specimens rather challenging. These stromatolite samples had me working hard.
The Irregully specimen depicted above left is roughly a foot overall, about 3 inches thick and weighs approximately 20.3 pounds. It wanted $150. The specimen above right is also roughly a food overall, about 3 inches thick and weighs about 10.8 pounds. It wanted $135.
Shown in hand above left and right are several nice chunks of Australian rhodenite which were among the most attractive to my eye among the selection of rhodenite shown atop one of Glenn's tables, which ranged in price from about $5 to $45. This material is from Tamworth, New South Wales, which Glenn related was about 250 miles northwest of Sidney. The piece shown in hand above left was about 6 inches across and about 2 inches thick and weighed in at a little over 3.1 pounds. It wanted $28. It will cut half a dozen or so very nice rhodenite slabs and is also chunky enough for carving. The piece shown in hand above right is about the same size and weight and it also wanted $28 to go home. This one was a tough call but after due deliberation the rock on the left picked me to take it home.
Depicted piled atop a table above left and in hand above right is black Australian jade. This nephrite is from near Paynes Find, Western Australia. The piece shown in hand above right is about 5 1/2 inches overall, over an inch thick and weighs in at about 1.8 pounds. It will cut 4 or more very nice slabs for cabs, inlay or intarsia or would also be suitable for carving. It was priced at $16 and this one went home with me.
Shown here is an unusual material with appeal as an interesting material for lapidary as well as specimens to collectors of petrified wood. This is peanut wood from the Cretaceous Windalia Radiolarite formation in the Kennedy Range of Western Australia near Carnarvon. Peanut wood originates from several varieties of wood with the principle one being petrified Aracauria (conifer) wood. The light colored "peanut" markings in this material are mollusk borings which have been filled with white radiolarian silt.
Peanut wood was washed into the ocean as driftwood where it was subsequently fed on by a marine shellfish called Teredo, which are also commonly known by the misnomer "shipworm". These bivalves bore tunnels into the wood and eventually pepper the entire piece with their boreholes. When the driftwood became waterlogged and sank to the bottom, it was covered with silt, filling the boreholes with radiolarian sediment. Eventually this material petrified and the Windalia was uplifted above sea level, liberating the peanut wood.
The prices I saw on Glenn's peanut wood ranged from about $3 to $70 depending on size. The half inch thick slab shown in hand above right was about 6 inches across and offered at $15. The chunk of peanut wood shown in hand at left was priced at $45.
Shown piled on a table above left and in hand above right is a red Australian jasper with hematite. Depending on the amount and distribution of the hematite in various pieces, this material varied in appearance from a metallic reddish gray to an intense red with dark metallic hematite stripes. Glenn reported that deposits of this material are extensive in Western Australia with a typical locality being Bullfinch. The chunk shown in hand at left was about 6 inches across, two inches thick and weighed about 3.7 pounds. It was priced at $25.
The material shown on table above left and in hand above right is known as mookalite. Mookalite is a silicified radiolarian siltstone. This colorful material is dug at Mooka Creek, in the Kennedy Range near Gascoyne Junction, about 100 miles inland from the town of Carnarvon. Mookalite specimens sometimes contain cavities left by decomposed belemnite casts or more rarely, impressions of ammonites.
Mookalite is revealed on the microscopic level to be principally composed of the remains of tiny organisms known as radiolaria, which possessed skeletal structures composed of opaline silica. Countless numbers of radiolaria were deposited as sediment in ancient seas which eventually consolidated as solid rock as they were cemented with silica, forming opalite, chert and chalcedony depending on the degree and type of silification.
I saw mookalite specimens on Glenn's table priced from about $2 to $26 depending on size. The piece displayed in hand above right was about 10 inches overall and priced at $18.
Depicted on table above left and shown in hand above right are specimens of orbicular granite. This material is found near Mount Magnet in the Murchison region of Western Australia. The orbicules consist of andesine, plagioclase, hornblende and biotite arranged radially around a core of plagioclase and/or hornblende or less commonly, mafic schist.
The specimens of orbicular granite shown on the table ranged in price from about $6 to $20, with the piece displayed in hand above right wanting $6. Orbicular granite has been quarried in large pieces for use as ornamental building material. With rockhounds it finds use as rough for spheres and other lapidary applications. These orbicules are also interesting to me as geological specimens, as the origin and process of formation of orbicular granite is still poorly understood and somewhat mysterious.>
Pictured piled on the table above left and in hand above right are pieces of an Australian material known as starry jasper. This material is pyritized and carbonate altered, metamorphosed, banded iron formation (chert) from near Meekatharra, Western Australia. I have recently cabbed some other pyrite laced material with very nice results so I decided to acquire a piece of this starry jasper for cabbing. The $13 piece shown in hand above right is about 5 inches overall, averages about an inch in thickness and weighs in at about 15 ounces. It had pretty good shape for slabbing and attractive distribution of the pyrite to my eye, so this one went home with me.
Shown piled on the table above left and in hand above right are pieces of an Australian material known as tiger iron. This banded iron material from the Ord Range near Port Hedland, Western Australia consists of a combination hematite, jasper and tiger eye. This is one of those materials you just can't do justice too with a still photograph due to the chatoyancy of the tiger eye which is apparent when the material is rocked to and fro slightly. Cabs cut from tiger iron can be very showy and eye catching although this is a messy material to work due to the hematite content.
Pictured piled on the table above left and in hand above right are pieces of a colorful Australian material known as munjina stone. Munjina stone is a silicified shale from the Chichester Range in Western Australia. The assortment of pieces on the table ranged in price from about about $6 to $30 depending on size. The nicely marked piece of Munjina stone shown in hand above right was about 4 inches overall and wedge shaped, varying in thickness from about 1/2" to 2". It will cut several nice slabs for cabbing and was priced at $15.
Shown above left is one of several boxes of Australian variscite slabs shown by Glenn. Variscite is a hydrated magnesium aluminum phosphate with a characteristic gemmy aqua-green color. Chemically variscite related to turquoise which has a copper component that variscite lacks. The country rock this material is mined from is a faulted, silicified shale that has been intruded by secondary quartz veins along with the variscite. Polished faces of this material exhibit aesthetic angular patterns and combinations of the variscite, quartz and shale. The variscite slabs shown in the box above left were priced from $3 to $45. The size of the box is 16 inches. Shown in hand above right is a variscite slab I thought pretty. It is about 6 inches across, 3/8 inch thick and wanted $16. Great bola tie material here... this piece would have gone home with me if my rough box wasn't still heavy with variscite acquired from Glenn at a previous Show.
In addition to slabbed variscite in boxes, Glenn also showed a table top piled high with variscite rough. These pieces ranged in price from approximately $2 to $165. Glenn related that so far there has only been one commercial variscite mining operation in Western Australia at Milgun station, which is a cattle ranch about 100 miles north of Meekatharra. The mine there was exploiting a horizontal seam running into the side of a steep hill. Unfortunately operations at that mine have ceased due the uneconomical amount of overburden which would have to be relieved to pursue the seam further into the hill.
Glenn and a friend have discovered another deposit of variscite over 100 miles from the discontinued operation. Needless to say I am looking forward to seeing this new material once the paperwork has been finished up on the mining lease for it and Glenn commences operations there.
Shown in hand above left is a 2.62 pound chunk of variscite I thought pretty. It was about 7 inches overall and about 2 inches thick. There were some cool cabs and bola tie stones in this piece which wanted $26 to go home. Pictured above in hand above right is a $6 slab of variscite that was about 3 inches across and 1/4 inch thick. Something about this piece spoke to me about a cabochon and so this one went home with me.
Shown at left is some porphyry rough and several slabs and spheres cut from this material. Porphyry is an igneous rock characterized by large mineral crystals called phenocrysts suspended in a finely crystallized groundmass. This Australian porphyry consists of pink feldspar crystals in a dark colored dolerite that originates from a greenstone belt within the Yilgarn Block, Western Australia. The nearest town to the locality is Cue, which is about 400 miles north of Perth. This material has been dated at approximately 2.9 billion years old. The porphyry slabs and rough ranged in price from about $8 to about $55.
Shown in hand below is one of about half a dozen spheres shown which were cut from this porphyry. I think spheres do a fine job of showing off this material. This one wanted $135 to go home.
Shown above left is a pile of Australian chrysoprase. Chrysoprase is a sought-after variety of chalcedony which is colored green by the presence of nickel, and more rarely chromium. A colloquial term for chrysoprase is "Australian Jade" due to its resemblance to some varieties of jade.
This material was offered at $20 per pound on a you-pick basis.
Pictured above right is a pile of gaspeite rough. Gaspeite is a carbonate that forms a solid solution series with magnesite, with gaspeite being the nickel bearing end member and magnesite being the magnesium bearing end member. This material came from the vicinity of Widgemooltha, which is located in a nickel belt in Western Australia and to the south of Kalgoorlie.
Gaspeite seems to be in vogue as a lapidary material due to its unique electric green color which is attributed to the nickel content. I'm afraid the intensely saturated, nearly day-glo color of this stuff is just too much for me generally, but there seems to be no shortage of others who are interested in buying and incorporating gaspeite in their lapidary work. Glenn related that the sole source of this material was a stockpile of ore accumulated and set aside during the course of a nickel mining operation, which has subsequently been exhausted. So there is no more gaspeite coming out and it is becoming ever rarer on the market. This material was commanding $80 per pound on a you-pick basis.
Glenn was showing some very eye catching pieces of "Marramamba", a sought after red tiger eye from an iron ore mining district in the Hamersley Range in the Pilbara region of Western Australia. Glenn related that maybe 20 tons of this material came out during the 1960s and then very little more except for a few tons he mined during the 1990s. It occurs in the Marra Mamba Iron Formation, which is the lowest unit of the Hamersley Group within the Hamersley Basin. The age of this material is approximately 2.6 billion years. It is composed of silicified crocidolite (blue asbestos) and associated with japer, chert, pyrite, magnetite and hematite.
The Marramamba slabs in the 16 inch box above ranged in price from about $5 to $45.
Pictured above left is another of several boxes of Marramamba slabs shown by Glenn. This box also measures 16 inches along an edge. These slabs ran larger than those in the previously depicted box and ranged in price from about $38 to $50. Shown above right is a Marramamba slab which is about 6 inches across that I thought had a lot of potential for cutting some upscale cabochons. This slab wanted $35 to go home.
At left is another Marramamba slab that caught my eye. This one is about 6 inches across and about 1/2 inch thick. It wanted $45 to go home. 1/2 inch is on the thick side for conventional cabbing but I can imagine a hybrid cabochon/carving cut from this material that would like this thicker slab.
Of course this material makes for beautiful specimen and display pieces just as they are without further lapidary work. In fact I have several slabs of Marramamba acquired from Glenn at a previous Show with the intent of cutting bola and belt buckle stones from them. I have cut one of the smaller pieces, which produced a fine bola tie stone. However I find I am having a very difficult time bringing myself to cut some of the larger ones. A paradigm case of wanting to have your cake and eat it too...
The magnificent Marramamba slab shown in hand above does a fine job of showing off the tiger eye component of this material, although this material really has to be viewed first hand to appreciate the chatoyancy. This one was commanding $90.
Australian Outback MiningArizona Mineral and Fossil Show at the Mineral and Fossil Marketplace (1333 North Oracle Road) - WWW: www.outbackmining.com Email: email@example.com PO Box 144 Mount Helena, Western Australia 6082 - Phone/Fax: +618 9572 1020
Art Africa and Minerals showed a number of tables piled high with malachite. Most of the material had been contour polished to show it off. I haven't done much work with malachite as a lapidary material myself, but have seen some very stunning examples of intarsia and other lapidary work incorporating malachite to good effect. Malachite is a copper carbonate, which at a hardness between about 3.5-4 is rather soft for use as jewelry stones worn on the hands or wrists which are subject to wear and tear from the inevitable banging about of hand worn jewelry.
Shown at the end of one row of the malachite covered tables were some very eye catching pieces of malachite with chrysocholla. The sky blue chrysocholla in this material really lights it up. This blue-green material was offered at $15 per pound and ranged in size from several ounces to pieces in excess of 10 pounds. Unfortunately the owner did not speak English very well and I did not speak his native language at all, so I was unable to obtain locality information from him for the malachite with chrysocholla any more specific than "Congo".
The piece in hand shown above right was about 5 inches across and weighed in at 1.18 pounds. While I noted some chrysocholla in this piece, it was mostly green and priced by the owner at $10 per pound along with the other "plain" green malachite, making this one an $11 rock. Note the boytroidal structure typical of malachite evidenced by the ringed patterns in this material. Zaire is a significant locality and source of malachite. Massive blocks of malachite have also historically been quarried in the Ural Mountains for architectural use as wall paneling and table tops as well as art objects for the Russian Czars.
However, not knowing the exact hole this material was mined from did not prevent me from snagging the wonderful piece shown in hand below. Many rocks whisper to me but this African beauty was screaming "Take me home Bob!" It is about 3 1/4" across and weighs 6.5 ounces. At $6 I just had to oblige it. I am still working out a game plan to cut a bola stone from this piece. But if it just wants to hang out with me as is for an extended period of time, that is OK by me too.
Art Africa and Minerals Arizona Mineral and Fossil Show at the Mineral and Fossil Marketplace (1333 North Oracle Road) - Email: firstname.lastname@example.org Kabongo Ndiadia, 7653 Ave. Kilwa, Lubumbashi, Rep. of Congo - Phone: 273.9702.5844
Depicted above left is a you-pick flat of "toenail" and small miniature sized garnet specimens that I happened upon while browsing at the InnSuites Hotel show. Out of a desire to provide a stronger focus for my mineral collection (i.e., finally out of space) than any species and specimen that appeals to my aesthetic sensitivities (that I could afford), I have recently been trying out a "leaverite" rule applicable to all species wanting to go home with me as specimens for my mineral crystal collection, except for quartz. And possibly pyrite...
However, shown above right is a pretty little $10 Chinese spessartite from the Tongbei Area, Yunxiao County, Fujian Province. Spessartine is the manganese-aluminunum member of the garnet group. The crystals on this specimen are translucent and light up with a nice glow and are large enough relative to the overall size of the piece to give the effect of a cluster, which is more interesting visually to my eye than a monotonous sea of druze. Now this one does appear to have a quartz component in some matrix that was still clinging to the back side of it, but I've already ruled that micro crystals in the matrix is really pushing it too far to describe something like this as "garnet on quartz" for the purposes of bringing it into my mineral specimen collection under the leaverite rule.
So I brought it in as rough for my rough collection. All this one needs is a little judicious grinding on the back side to remove most of the matrix and reduce its thickness somewhat to transform it into a naturally formed gemstone serving as the focal point for a unique piece of jewelry. This one may want a lost wax cast piece to mount it, so as to achieve a very precise fit of the silver around the perimeter of the specimen, err gemstone I mean...
Need more input? For additional information on gemstones and lapidary materials be sure and check out the Books about Gemstones and Books about Lapidary in the References for Rockhounds catalog at Bob's Rock Shop!