A curious piece of folk art, a statuette of a bear carved with a power tool from a dense rock, a granular massive sulphide ore. Object loaned by Jim Connor. The piece weighs 877 grams and measures 17 cm from nose to (beyond the) tail.

"Rock of the Month # 97, posted for July 2009" ---

A massive-sulphide rock carving, which at the initial time of writing was of unknown origin. The rock itself is granular and massive (i.e., lacking obvious directional structures, however caused), the grain size 1-2 mm. At first thought to be pyritic, on re-examination the sample shows a dappling between light and dark sulphide. The material is composed of approximately: 1) 15% pale pentlandite, an important nickel-iron sulphide with octahedral cleavage traces and a uniformly pale colour, mostly 1-2 mm across but occasionally as clots or "eyes" to 10 mm; 2) 60% dark-tarnishing pyrrhotite, a darker iron sulphide; 3) 23% of a fine-grained ferromagnesian silicate matrix, the "gangue"; and 4) 2% tawny yellow chalcopyrite, a copper-iron sulphide. The chalcopyrite indicates appreciable copper tenor, while the pentlandite is consistent with a magmatic sulphide ore rich in nickel, such as those won from the major mines in Sudbury, Ontario for nickel, copper, platinum-group elements and other associated metals.

The piece appears to be carved from a single piece of ore, with small ball bearings for eyes. The beast is cute, or perhaps scary - probably an attempt to continue the old human tradition of making bears into bogey-creatures from our ancestral fears (for a counterpoint, see the web site and especially the northern Minnesota home of the North American Bear Center).

The carving of rocks and minerals into artwork dates back into antiquity. Sometimes rocks such as marble or shale furnish the raw material (Kempe, 1983). Softer minerals and organic materials are also popular, such as soapstone (rich in talc), pyrophyllite and jet. Jade is a staple in Asian works, as is soapstone in Arctic Canada. Other semi-precious stones and gemstones may also be carved, e.g., garnets, quartz, sodalite, tourmaline and ruby (red corundum, as hard as talc is soft!): see Miller and Sinkankas (1994), and the annual catalogues of the Tucson Gem and Mineral Show, published by Colored Stone. The artisans of the German district of Idar-Oberstein are especially renowned for detailed carvings of challenging materials, such as ruby with zoisite from east Africa (Yonick, 2008; see also example in White, 2008). Fossils may also be carved ("improved upon", or faked for profit): both ancient and modern examples are known (Gould, 1998). My own favourites are ammonites found in England ("relics"), to which some long-dead artist carved an imagined head for the much longer-dead original inhabitant of the shell.

Peter Ellero

The artistic and geological origins of this piece were something of a mystery: the former has almost certainly been solved by the bear's owner, Jim. He found a smaller bear of identical style, mounted on a base of orange onyx (from Mexico or Brazil?), forming an attractive commemorative plaque. This smaller statuette is attributed to Sudbury, Ontario artist Peter Ellero, who also crafted a splendid penguin statuette, in a contrasting buffed finish. Mr Ellero, it turns out, was a stone-cutter in Italy, and moved to Canada, first crafting some good curling stones of `black granite' from the River Valley area, before becoming an underground miner at Sudbury in 1967, working in Inco's Creighton mine. With a natural flair for his craft, passed down from his father and grandfather, he was soon turning out all manner of trophies, jewellery, bookends and other pieces in his own well-equipped workshop (Anon, 1968). This work was eventually continued under the mantle of Peter Ellero & Son Limited, first in Sudbury and then in Little Current, Ontario.

Geological origins

The penguin was also evidently sculpted from a magmatic ore, dominated by the iron sulphide pyrrhotite, with 2% chalcopyrite found largely as streaks around the small mafic inclusions. It displays many mm-sized rounded clasts of granitic material, largely quartz, plus fine-grained greenish-black mafic melt. This is probably inclusion-crowded "contact ore" from low in the Sudbury basin. The 708-g piece has high magnetic susceptibility (~34x10^-3 SI units) and attracts a pen magnet strongly. Source: Montland Books, Williamsford, Ontario.

The two bears, in contrast, are formed of equant granular sulphide, evidently rich in pentlandite with lesser chalcopyrite in pyrrhotite. Their raw material (equally magnetic, ~34x10^-3 SI units) is presumably from an orebody in the "Sublayer" of the Sudbury igneous complex.

A third Sudbury ore type, and a very economically important component, is the so-called "deep copper veins" in the footwall of the Sudbury structure. Massive sulphide ore is very rich in chalcopyrite, and has a much higher Cu/Ni ratio and elevated precious-metal content relative to typical Sudbury ores. A piece of such ore (sample 2259, Strathcona mine) is extremely dense, essentially solid chalcopyrite, and very magnetic (~60x10^-3 SI units), presumably due to unobtrusive magnetite and Ni-Fe sulphides.

The initial thought of pyrite was suggestive of the Errington and Vermilion Lake mines, which worked pyritic copper- zinc- lead- (silver, gold) ores deposited underwater in the western Sudbury basin, in the aftermath of the asteroidal impact event which generated the Sudbury structure and allowed for the emplacement of the magmatic nickel ores. Although spatially close, these rocks are quite distinct in mineralogy and origin from the high-temperature magmatic nickel ores of the famed Sudbury camp. A large slab of this sedimentary exhalative (sedex) ore (sample 2445, Errington mine) would not attract a pen magnet (~0.5x10^-3 SI units), lacking the highly magnetic nickel sulphide assemblage, and also evidently with little or no magnetite.

This pair of carved loons (above) are a playful representation of a favourite Canadian waterbird (the common loon, Gavia immer). The ore is rich in pentlandite, pyrrhotite and chalcopyrite, the latter tarnished to a dark tawny hue, a pleasing effect against the dark host rock. The charmingly long- and short-billed little sculptures (133 and 143 g in weight) are significantly magnetic, bulk magnetic susceptibility at least 12.4 and 9.0x10^-3 SI units, respectively. Source: Ted Joiner, Victoria, B.C.

The Sudbury ores and regional environment have been described in great detail over the years (see. e.g., Pye et al., 1984; Roussell and Jansons, 2002). By the end of 2014, the MINLIB bibliography contained some 1,400 articles to the area and its famed mineral deposits. An interesting recent article describes the environmental mineralogy of the largest burning yard operating in the sulphurous "bad old days" of Sudbury, when open-bed roasting was employed, 1888 to 1923, as a preliminary to metal refining of ores dominated by pentlandite, chalcopyrite and pyrrhotite (Schindler, 2014). The roasting drove off much S as SO₂, largely by oxidation of the pyrrhotite, resulting in legendary pollution and environmental damage, the amelioration of which has been addressed in the past 50 years.

In conclusion, each of these pleasing sculptures was almost certainly crafted from ores of the Sudbury area which, for more than a century, has been Canada's top supplier of nickel and byproduct platinum group elements, and a major source of other metals such as copper and cobalt.

With thanks to Jim Connor, and to Ryan Weston, who provided some Sudbury insight into the metal menagerie.

References

Anon (1968) He can see dancing girls in the muckpile. Inco Triangle 28 no.6, 14, September (see the archive of this trade magazine, produced from 1936 to 1998, at the Sudbury Museums web site).

Gould,SJ (1998) The lying stones of Wurzburg and Marrakech. Natural History 107 no.3, 16-21,82-90.

Kempe,DRC (1983) The petrology of building and sculptural stones. In `The Petrology of Archaeological Artefacts' (Kempe,DRC and Harvey,AP editors), Clarendon Press, Oxford, 374pp., 80-153.

Miller,AM and Sinkankas,J (1994) Standard Catalog of Gem Values. Geoscience Press, Inc., Tucson, 2nd edition, 271pp.

Pye,EG, Naldrett,AJ and Giblin,PE (editors) (1984) The Geology and Ore Deposits of the Sudbury Structure. OGS Spec.Vol.1, 603pp.

Roussell,DH and Jansons,KJ (editors) (2002) The Physical Environment of the City of Greater Sudbury. OGS Spec.Vol. 6, 228pp. plus 3 maps.

Schindler,M (2014) A mineralogical and geochemical study of slag from the historical O'Donnell Roast Yards, Sudbury, Ontario, Canada. Can.Mineral. 52, 433-452.

White,JS (2008) Herbert P. Obodda: dealer, gentleman, and collector extraordinaire. Mineral.Record 39, 315-330.

Yonick,D (2008) The fine art of survival. Colored Stone 21 no.2, 34-38.