Anders Adolf Retzius (Stockholm, Sweden) was the first to describe the beautiful markings on elephant ivory known as ‘lines of Retzius’; today gemologists describe it as 'engine-turned' pattern in ivory.
According to Robert Webster, they appear as ‘striae of different shades of cream proceeding in the arc of a circle and forming by their decussations (lines crossing to form overlapping ‘X’ patterns) minute curvilinear lozenge-shaped spaces which appear like an engine turning…..These ‘lines of Retzius’, as they are called, are seen only in ivory from the elephants, and are not apparent in ivory from the other animals….The engine turning (pattern of overlapping X’s) is not seen in the imitations, and provides a certain check on the piece being ivory. The lines of Retzius…are due to the dentine being permeated with fine thread-like canals filled with a brownish gelatinous substance, which in life conducts the nerve fibrils. These fine canals extend outward from the pulp (central nerve and blood vessel) cavity of the tusk in flattened spirals of opposite hands, and it is these dense pores with their gelatinous contents which give to ivory its beautiful polish and exceptional elasticity.’ (Webster, 1983, p. 590)
The experts believe the dentine portion of ivory is roughly 70% mineral matter (mostly calcium phosphate in the form of apatite) and 30% organic matter (collagen, a complex protein), while enamel is roughly 99% mineral matter (mostly apatite) and 1% organic matter, making it durable and hardnest substance produced by the body (human/animal). Elephant ivory from traditional sources + ivory from extinct elephant species such as the Mastodon and Mammoth + the teeth of hippopotamus, walrus, narwhal, sperm (or cachalot) whale, wild boar and wart hog may be used for jewelry and works of art.
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