WOOLLY mammoth tusks are often the top lot of the fossil section of Sotheby's sales of 'Garden, Architectural and Fossil Decoration'. Fossils have always had a following from collectors, but their increase in popularity may be a result of the art world's move into the natural, deathly, sensational and anatomical, by people like Damien Hirst. Movements in art influence exterior and interior design, and fossils are one of the nearest things you can get to tasteful and naturally decorative sculpture made into durable materials from the death of animals and plants. Death and anatomy are recurring themes of Britpop. Fossils are perhaps a more acceptable way to represent them. Fossils are attractive because they will fit with stark minimalist interiors as well as junk-filled maximalist ones, although I have never seen a millionaire's retreat with interiors tastefully decked out in ammonites, trilobites, knightia fish and the odd mammoth tusk (publishable photo's gratefully received).
 
Fossils are strictly-speaking mineralised organic matter, which means living things turned to rock. Although you can find fossilised mammoth tusks up to 1.6m years old, those sold at auction tend to be real 20,000 years old ivory that has been preserved by being buried, often in bogs or alluvium, where the lack of oxygen has prevented their natural decay. Mammoths became extinct 3,500 years ago due to global warming and hunting by paleolithic man.
 
The recent global warming in places like Siberia results in melting ice and tundra, and soil erosion which exposes buried mammoth skeletons. Greater mineral exploitation, small aircraft, quads and four by fours, general mobility and local awareness of value, means more and more fossils will find their way to the relatively rich western markets.
 
Practically anything removed and sold results in accusations of desicration and profiteering. The world of architectural and garden antiques is familiar with that sentiment by conservationists. Now archaeologists are at loggerheads with fossil-hunters. A long ethical argument is described in the story of Confuciusornis sanctus in China, where fossil hunting is banned. In most parts of the world, collecting fossils from private land with the owner's permission is perfectly legal.
 
Butterfields in San Francisco is an auction house well known for its regular architectural and decorative antiques sales, where fossil selling has generated more of a public debate between academics and fossil-hunters. In 2001 a Siberian woolly mammoth tusk sold for $32,000 at Butterfields.
 
Woolly mammoth tusks have another ethical dimension: they are real ivory, and new ivory trading is protected under CITES regulation. However the sale of antique and prehistoric ivory is unregulated. How do you tell elephant from mammoth ivory? A section through both elephant ivory and mammoth ivory show natural cross-hatching. The angle between the cross-hatches can be an absolute test, outside the range 90 degrees - 115 degrees. Between these two figures a precise indentification is impossible. Clearly with single tusks this test will not work, unless a section has been cut and polished.
 
Whole mammoth tusks tend have flattened ends, roughly the last third towards the points, and have are often marked and worn on the undersides where it is believed they were used for foraging. They frequently wrapped inwards towards each other. Male tusks are thicker, more three-dimensionally curved and longer than female tusks. The longest mammoth tusks discovered are 16ft long.
 
How do you tell real ivory from bone or resin replica? Much of the real ivory antique netsuke replica is carved in workshops in Hong Kong. The Asian Arts website describes, not only the hot pin test to tell the difference between ivoyr and resin, but also whether it is real ivory (hardenend dentine) or plain bone. It also gives pointers as to which animal the ivory may come from. The test is to take a pin or large needle, or large straightened out safety pin, and heat the tip red hot, then stick it into the item. If ivory, the pin will not penetrate but will only leave a tiny mark. If resin, it will go straight into the item and leave a raised area around the hole. If ivory, the smoke will smell of drilled tooth that you get at the dentist's. If it smells like burning plastic, it is resin. Bone is resistant to heat, but not as much as ivory. The smell is less (or hardly at all) and is different than that of burning tooth. Bone is free of grain and will always have little "pock marks" (sometimes brown) where the marrow was, visible with a magnifying glass. If it has any grain, especially crosshatching, you have the real ivory. Planet Ark the eco-website says, 'Mammoth ivory, now starting to come onto the market in large quantities as global warming thaws the permafrost in Canada and Russia and exposes the corpses of the long-dead woolly giants, is virtually indistinguishable from elephant ivory. However, unlike elephant ivory, mammoth tusks smell, and are harder to work.'