Homer Thiel & anyone else interested in bone v. ivory:  I found this issue
cropped up again & again in studying artifacts of needlework & sewing.  I'm
at home & don't have all the sources on artifact identification immediately
to hand, but I do have something that might be of use.  Let me quote at
length from one source on needlework tools:
 
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The difference between bone and ivory is not always evident.    They are
chemically similar and have tubular cells running lengthwise.  Both yellow
with age, grow brittle, and are subject to warping. Tthe difference appears
when they are cut open.
 
Bone contains small channels which once carried blood.  When bone is cut
across the end, these small channels appear as very small dark holes.  When
cut lengthwise, the channels are exposed as long dark lines.  When turned
on a lathe, the small channels are penetrated and exposed as pitted areas.
Looking at bone through a magnifying glass will reveal a pitted surface
that is less shiny and more opaque than ivory.  Elaborate carving makes
visual identification more difficult as it tends to conceal those surface
characteristics which differentiate bone from ivory.  The collector will
find that more needlework implements have been made of bone than of ivory
as bone is more plentiful and cheap.  The shin bones of horses, cattle and
sheep have been widely used because of their large size and minimum cost.
 
Ivory from the tusks of elephants is more dense than bone and is made of
the same hard material, dentine, as is the human tooth.  When ivory is cut
in a cross section, the characteristic arc lines, made up of the cut ends
of very minute tubes radiating out from the centre are clearly visible.
This profusion of overlapping circles has been called the "engine-turned"
effect.  When cut lengthwise, ivory reveals long, parallel lines
alternating between a lighter and darker effect.  Some of these lines are
straight while others are wavy.
 
Ivory takes a better shine than bone because the tubular structure of the
ivory, when alive, was filled with an oil-like substance.  This also
explains why old pieces of dessicated ivory often take on a new life when
polished with oil.  Ivory is also porous and takes stain very well whether
intended or not.  It also bleaches strongly when exposed to sunlight.
 
There are imitations of ivory such as ivorene made of ivory dust, glue and
other ingredients.  Ivorene lacks the characteristic striations and lustre
of ivory.  More common is the plastic, celluloid, inveted by an Englishman,
Alexander Parkes in 1862.  This first artificial polymer was made of
xylonite cellulose nitrate stabilized with camphor, and was often referred
to as xylonite.  An improved form of celluloid by the American, John Hyatt,
in the 1870s, made the product commercially feasible.
 
Celluloid may appear to have a grain like ivory and bone.  This grain is
achieved by casting celluloid in thin layers of alternating shades of an
ivory colour.  It is not like the grain of any natural substance.  The
grain effect appears the same however celluloid is cut because it has
neither a natural cross section or length.  Moreover, celluloid as a
thermoplastic material is subject to melting when touch by fire which does
not affect ivory or bone in that way.
 
from:  An Illustrated History of Needlework Tools by Gay Ann Rogers
(London:  John Murray, 1983), pp. 70-71.
 
I have an article on bone comb manufacture in Byfield, Massachusetts in a
publication by the Essex Institute (in my office) that I can provide a
reference for on Monday (it's a special issue of the Essex Institute
Historical Collections).  I recall a recent article in IA (journal of the
Society for Industrial Archeology) on ivory used for piano keys that may
have more about identification of ivory vs. bone but can't recall that
level of detail.  I'd also recommend Geoff Egan et al.'s Dress Accessories
volume in the Museum of London series on finds from London (this is in my
lab at BU at the moment; I THINK it has something on bone combs from
medieval deposits); the Norwich Households volume also has a section on
crafts.   I'm sorry to be incomplete with these references, but can
certainly flesh them out if you think the information might be of use.
 
I suspect that ivory combs would fall into the category of personal
adornment & be used to "decorate" as well as hold the hair as back & side
combs rather than as nit combs &c., given the relative cost, but this is
just a guess.
 
 
 
 
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Mary C. Beaudry
Editor, Northeast Historical Archaeology
Associate Professor
Director of Graduate Studies
Department of Archaeology
Boston University
Boston, MA 02215
 
tel. 617-353-3415
fax. 617-353-6800
email [log in to unmask]
 
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