Re: Large cities at time of contact Re: diseases and immunity
Thu, 04 Jul 1996 09:15:17 -0700

Philip Deitiker wrote:

> The issue is that although most deposits are not going to be of good
> quality (on average) if one is careful one can find pieces which are
> highly silicate enriched and in some areas cooled properly.

Yes, one can find volcanic glass with fewer impurities, but silica content does
not vary widely from one sample to another. It is differences in silica content
that determine the type of volcanic glass (ie obsidian 70%, although I think it
might be proper to allow for a +/- 5% on this. However, the same would apply to
silicates. Even manufactured glass can be expected to have some variation.)

>The rate
> of cooling in natural pieces is going to depend on size and
> surrounding insulation. Manufactored glass, from what I've seen is
> cooled over about 12-24 hours, which is part of the range of cooling
> in natural pieces.

The rate of cooling is not the point. Natural glass does not cool at an even rate.
Manufactured glass is cooled evenly.

>So I'de have to say if an industry was specialized
> enough to know where to look and how to discern, say, from several
> tons of deposit, which few pounds of pieces where most reliable and
> learned how to make refined and useful impliments, kudoos to them.

Obviously there was some degree of specialization. The ability to identify quality
stone would be expected.

> Sorry, the glass blades for sectioning have been traditionally made
> via encouraged fracturing (laser technology is out of the $ range for
> most biological work) really not much different than the aztecs did.

Laser cut blades would not be that expensive, no more so than a lense. Fracturing,
even with modern technologies, seems a highly unreliable way to develop a blade.
However, I will have to take your word on the processes involved.

> Take just about any piece of glass irregardless of quality but
> definable as glass and your going get a very sharp edge. Glass edges
> differ from metal edges because metal polishing produces microscopic
> ridges which incourage tearing as apposed to slicing. I could have
> easily used a section of a new aztec knife for sectioning and get high
> quality sections. Loan me one for a few years and I'de be happy to
> give a demonstration (grin).

The same concept you apply to glass here applies to blades from silicates and

> As far as the sectioning knives are concerned and how they compare
> with the aztec knifes the desire is pretty much the same, what one
> desires is to begin the fractoring process at the right angle to get
> an edge within a small acute angular range. Too acute and the blade is
> brittle, to steep and its cutting capacity is diminshed. For
> sectioning its easy becasue only an inch or so is required, for the
> aztecs a blade of a foot or so relatively strait and maintaining its
> angle must have taken great skill to obtain.

I have never even seen a flint blade over six inches. Were there really glass
blades this long? It seems highly improbable.

> You really beleive this? Esoterically yes, but functionally I think
> one has to understand the behavior of glass in order to get a desired
> result.

This is why it is important to recognize glass as a supercooled liquid rather than
a solid. It is this factor which gives glass it's unique qualities. My only point
was that if you are going to present a scientific explaination of the differences
between glass and silicates, accuracy should be considered.

Whatever the understanding, there still is no major difference in the production
methods used on volcanic glass and that used on silicates.

>>While I have not seen any Aztec glass blades,

> Then maybe you should, before you talk, they are quite impresive.
> You'll see what I mean about sharpness.

I don't need to see a blade to understand the physics involved in the production
of such blades. The quality of the craftsmanship does not change the basic nature
of the materials used.

I do not doubt the sharpness. I often rely on flint over steel for this reason.
However, when it comes to maintaining that edge, even Pyrex does not compare to
quality flint. The only thing preferable to flint for this purpose would be fused
silica, unfortunately, it is also too expensive to experiment with.

>> I have seen their work with jade and flint.

> When glass fractures it gives much longer strait edges as apposed to
> flint. flint may be preferable for short instruments, but glass is
> preferable for longer instruments.

In this you are far off base.

First, flint fractures in a similar manner to volcanic glass. The primary
difference is that flint blanks are drawn by striking close to the edge of the
core, while glass would fracture if the strike took place to close to the edge.
Glass blanks are not usually as sharp as flint at this stage (the angle of the
strike plays the same role for both stones. A 90 degree strike will not only
produce a sharper blade, but also a shorter one). After the blank is drawn,
pressure flaking is used to refine the edge of the blade. Both the flint and the
glass blade will be equally sharp (depending on the skill of the craftsman).
However, even in the earliest stages flint begins to stand out as a superior
material. The brittleness of the glass increases the chance of error (stone is a
very unforgiving material to work with).

Second, the length a blade can reach and still function reliably is dependent on
the strength of the material used. Flint (between 6 and 7 on Moh's scale) is much
stronger than volcanic glass (between 5 and 6 on Moh's scale). (Note: the ranges
allow for the existance of impurities in some samples. Thus, a high grade obsidian
blade will be almost equal in strength to one made of a low grade flint).