chrish@videovax.tv.tek.com (Chris Hawes) (10/24/90)
I'm seeking info on how to distinguish the difference between carved and polished bone vs. carved and polished ivory. I have an antique that I have been told is worth 3X more if its ivory. The antique is a vintage Mah Jong game made in the 1920's. I took it to one biology teacher, but she said the polishing made it difficult for a non-expert to tell whether or not it was bone. I would especially be interested in any info regarding the economics in the 1920's which would have in- fluenced the use of bone vs. ivory. Obviously, the cost of ivory today is very high, but what is the cost of bone? And what type of bone would have been used at that time to make handcrafted items? Should I trust an antique dealer with this question? How difficult is it to tell the difference? Pursuing this has lead to revealed some interesting points such as walrus ivory is "legal" to sell only if it has been harvested and carved by an Eskimo. Thanks in advance, chris
larry@kitty.UUCP (Larry Lippman) (10/27/90)
In article <6102@videovax.tv.tek.com>, chrish@videovax.tv.tek.com (Chris Hawes) writes: > I'm seeking info on how to distinguish the difference between > carved and polished bone vs. carved and polished ivory. I have an antique > that I have been told is worth 3X more if its ivory. The antique is > a vintage Mah Jong game made in the 1920's. I took it to one biology > teacher, but she said the polishing made it difficult for a non-expert > to tell whether or not it was bone. Old ivory has a higher percentage of collagen (like 30% or so) than old bone (like 10% or so). The density of ivory has little variation from 1.9 g/cm^3, while the density of bone varies between 1.7 and 2.0. A density much higher or lower than 1.9 can be used to *exclude* the presence of ivory. Density can be non-destructively measured using water displacement. An experienced person can usually tell the difference between ivory and bone by visually examining its fluorescence under UV illumination. As I understand it, ivory has a more pronounced fluorescence, with "newer" ivory being purple and "older" ivory being mottled yellow. The above fluorescence is different from that of bone. Chemical analysis can also be used, but I suspect it is not necessary for your application. > I would especially be interested > in any info regarding the economics in the 1920's which would have in- > fluenced the use of bone vs. ivory. Obviously, the cost of ivory today > is very high, but what is the cost of bone? And what type of bone would > have been used at that time to make handcrafted items? Sorry, but these questions are definitely out of my field! > Should I trust an antique dealer with this question? Contact a museum or university to locate someone with a specialty in archeology, anthropology, paleontology or antiquities conservation for an impartial determination. > How difficult is it to tell the difference? Probably not difficult for an experienced person. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 {utzoo, uunet}!/ \aerion!larry
jfm@hasty.med.unc.edu (John F. Miller) (10/29/90)
In article <6102@videovax.tv.tek.com> chrish@videovax.tv.tek.com.UUCP (Chris Hawes) writes: > > I'm seeking info on how to distinguish the difference between >carved and polished bone vs. carved and polished ivory. . . Bone and ivory have very similar characteristics in terms of refractive index, hardness, specific gravity, and general appearance. The primary means of differentiation involves microscopic observation. At 20X-50X, bone shows minute cavities (lacunae) or dark bands, depending on the orientation. Elephant ivory displays a unique "engine-turned" appearance on cross section due to the spiral structure of the tusk. Elephant ivory may also display straight or curved grain lines or wavy canals. Ivory from several other sources (hippopotamus tooth, wart hog tusks, narwhal tusks, sperm whale) more closely resembles elephant ivory than bone, but the differences in appearance are generally rather subtle. There are also two vegetable products that resemble ivory -- corozo nut and doum-palm nut; they can usually be differentiated by refractive index or specific gravity. Consult your local gemologist for more details (shop around, though, since the average jeweler will not likely be able to tell the difference). >. . . Obviously, the cost of ivory today >is very high, but what is the cost of bone? And what type of bone would >have been used at that time to make handcrafted items? Should I trust >an antique dealer with this question? How difficult is it to tell the >difference? Actually, the cost of ivory has plummeted over the last couple of years, since international trade of elephant ivory has been banned by most nations, and public demand has dropped due to elephant conservation efforts. The cost of bone (usually cow bone) is minimal. Most of the value of finished items now is a function of labor and artistic merit. I would advise you to consult with not one, but several antique dealers who frequently do business with this sort of item. In the world of antiques, as elsewhere, "90% of everything is crap". Take several opinions and ignore those that do not have the ring of truth. -- John Miller, Gemcutter/Graduate Gemologist (oh, yeah, and Analyst Programmer) John F. Miller Department of Pharmacology, UNC-CH School of Medicine 1026A FLOB (231H) CB#7365, Chapel Hill, NC 27599 Tel: (919) 966-6966