Leif, I think your suggestions are right on -- nobody was making a comb
out of this bone, though it might still have been a 'blank' for making
cloak pins or game pegs or somesuch. But as for demineralization: I see a
certain number of demineralized cattle metatarsals at Vindolanda. Most of
our bone is permineralized, but anything that comes from a
shallowly-buried context, where it was not 'sealed' into an anaerobic
stratum by a packed clay overlayer, will be rotten or semi-rotten. And
what this produces, in my experience, is not the kind of cracks seen in
your specimen Martyn but 'exfoliation', where the dense peripheral bone
flanges out and peels away from the more interior spongy substance. I have
never seen the exfoliating layer be thicker than about 3 mm., and the
plane of separation is at 90 degrees to that in Martyn's specimen, i.e. it
is annular. And, as soon as the peripheral layer begins to exfoliate, it
seems that the spongy or 'spongier' substance interior to it quickly
becomes very friable and, when subjected to the least pressure or
movement, falls apart into powdery crumbs. In hanging around abbatoirs and
farmers' bone piles and so forth I have seen a fair amount of 'busted'
bone, and I agree with Leif on this point too, that Martyn's specimen
split, or was split, after it had 'aged' a certain amount of time; it was
not 'bone dry', but it was not 'dead-green' either, and it did not have
the hide still on when it happened. -- Dr. Deb
> Hi Leif
>
> No the cracks are certainly not straight as if sawn. The cause of the
> marks are something else. There could well have been something on the
> inside of the bone though I don't think I see any evidence of it
> remaining.
>
> That the bone had become slightly de-collagenised had crossed my mind. No
> other bone from the context shows very similar signs of preservation.
> There is certainly nothing else which has split like this, so, if it has
> been through some other process, it may have mixed in with other bone when
> it was deposited.
>
> Glue-making sounds very intriguing though I have no idea of the history of
> this practice, if at all, in the early 1st centuries AD in Britain.
> Anybody?
>
> This is becoming very interesting though.
>
> Cheers,
> Martyn
>
>
> ------Original Message------
> From: Leif Jonsson
> To: [log in to unmask]
> To: Martyn Allen
> Subject: Re: cattle metatarsal
> Sent: 21 Feb 2011 07:34
>
> Hi,
> to me this does not look like sawing or cutting with a burin (or other
> cutting tool). I believe it is some sort of cracks. I have experince from
> Iron Age and medieval comb making in antler and bone and mesolithic bone
> and antler working. A metal saw produces straight furrows with lines from
> the saw teeth going at right angle to the furow. Sawing lengthwise in a
> bone includes sawing the opposite side of the bone, unless it was split
> half in the frontal plane. Making forrows with a burin produces even edges
> of the furrow with lengthwise strie from the cutting tool edge (metal or
> stone).
> Looking close on the furrows of your metatarsal bone you can see that they
> are not straight but rather stepwise. I don't believe that the bone was
> quite fresh when the ?cracks? came about. Are there any signs of pressure
> from the inside? As if there had been a stone or metal tange put inside.
> De-collagenized bones left over from glue making easily split along
> direction of osteons, but such bones also flakes from surface and inwards.
> Is there a tendency of splitting among ther bones from the same context?
> Hope I haven't confused you too much.
> Leif Jonsson
> Gothenburg Museum of Natural History
>
>
>
>
>
>
> From BlackBerry smartphone from Virgin Media
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