Friday, February 26, 2010

What Is It? - Part 2

Last week we posted a new blog section titled “WHAT IS IT” where viewers have the opportunity to present their comments about an unusual artifact. Future “WHAT IS IT” postings will include unusual objects of prehistoric and historic age that are not typically found in the archaeological record. Last week’s artifact was the so-called “ceremonial pick”, a unique symmetrically shaped bi-pointed stone tool. We have seen five examples and there are undoubtedly many more out there to be discovered. One of our readers suggested that the “ceremonial pick” is not a prehistoric artifact at all but a sharpening stone manufactured from compressed graphite used to sharpen scythes. Indeed, we at TWIPA agree that the object is a sharpening stone, but a stone, used to sharpen a different type of tool.

We were so interested in this object that we contacted the Department of Conservation and Natural Resources Bureau of Topographic and Geological Survey’s John Barnes, Geologist Supervisor in the Resource Analysis Section to determine the elemental composition of the object. We provided John and his colleague, Steve Shank, with two samples from two different specimens which they analyzed via SEM (scanning electron microscope).

Their findings were amazingly detailed! As it turns out, both samples contained aluminum oxide (corundum); silicon oxide (quartz); iron oxide (hematite) and a trace of manganese. In addition, Steve determined that naturally occurring corundum would not be stable with quartz under geologic conditions. The corundum plus quartz would normally react to form one of the aluminosilicates.

This is where it gets interesting! Since John’s SEM analysis clearly indicated the presence of corundum and quartz in both sample matrices, the parent material must be something other than natural stone. John discovered that “ …… based on the data that we have that indicate the apparent presence of both aluminum oxide and silicon oxide in both sampled stones, I am now leaning toward this being some sort of man-made mixture of quartz and corundum, both which are abrasive minerals, perhaps in some sort of an iron casting”………..

In addition, we consulted with Robert Smith, Geologist DCNR (retired), who has been among the pool of experts called upon in our never ending analytical quest of the “odd and unusual.” He provided insight into a possible method of manufacture and use of these sharpening tools. Bob states, "[the material] was molded and then fired at moderate temperature. Clay is a possible, cheap binder, which would not have required heating to the point where the corundum and quartz would react in a dry system…. Contemporary brand slipstone say they use Japanese corundum and a ceramic [after heating process] binder. They are probably fused until almost a porcelain ..."

Which leads us to solving the mystery of the ceremonial pick featured in last week’s “WHAT IS IT”. The bi-pointed stone tool is a commercially manufactured slipstone used for sharpening a woodworker’s steel gouge!

For more information, visit or the Hall of Anthropology and Archaeology at The State Museum of Pennsylvania .

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