Thoughts on "G"

It’s been a topsy-turvy week here at TWIPA, and if any of our readers are in the Harrisburg area they know what we’re talking about. After an abbreviated Monday, a cancelled Tuesday, a late start and an early dismissal on Wednesday (all due to the city’s water woes), we’re anxious to get back in the saddle and return to a schedule that bares some semblance of structure and order, that, after a few days off, we find ourselves oddly in need of. So as we continue our alphabetical journey through all that is archaeological, we arrive this week at the letter “G”.


Rather than “G” being for,”Gee, I wonder if the Capitol Complex will be open tomorrow.” it can instead represent ground stone objects. A number of this type of artifact have been featured in previous posts such as; grooved and multi-grooved stones, a cache of celts from the City Island site, adzes used to construct a replica dugout canoe, and chunky stones or discoidal artifacts. All of these posts include excellent examples of ground stone artifacts, and have been linked here for your convenience for you to peruse at your leisure. While not an exhaustive list, it does go far in illustrating the wide range of artifacts typically referred to as ground stone.

ground stone tools: hafted adzes left and right, grooved and hafted axe in center

The essential difference between ground stone tools and their counterpart (chipped stone tools) is in their style of manufacture. Ground stone tools are shaped by pecking, grinding, and finally, polishing the surface to achieve the desired form. This method is in stark contrast to chipped stone tools, which are, as the name suggests, chipped, or flaked, into shape through concoidal fracturing.

To muddy the waters a bit, there are some artifacts that display characteristics of both methods, for example a chipped stone projectile point with a smooth base from basal grinding, or an unfinished axe blade exhibiting large flakes removed during initial rough shaping prior to the intensive process of pecking and grinding. In these examples, it can be comfortably argued that the majority of the labor expended in each technique to produce the finished tool, would place the projectile point in the chipped stone category, and the axe as a ground stone object.

We’d be remiss however if we did not note that the letter “G” and archaeology have much more in common than just gorgets and grinding stones. Emphasizing that archaeology is an ever increasingly multidisciplinary endeavor, ”G” can also stand for; geography, geology, geomorphology, genetics, global positioning systems (GPS), geographic information systems (GIS), and ground penetrating radar (GPR). These fields of study and survey techniques (and many others that don’t happen to begin with the letter G) can all play an important role in enhancing our understanding and interpretation of archaeological sites in the 21st century.

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

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 PAarchaeology.state.pa.us or the Hall of Anthropology and Archaeology at The State Museum of Pennsylvania .