Sample Submission
Obsidian Hydration Analysis Selection Considerations
Larger numbers of analyzed artifacts will produce results that are statistically more significant. The factors that influence the formation of a hydration rim over time are complex and even specimens manufactured at the same time are unlikely to all develop hydration rims of identical dimensions. This is one of the reasons that we recommend that rim values be used primarily as a relative, not an absolute dating method. Larger numbers of measurements are more likely to reveal accurate temporal trends and are less likely to be influenced by outliers. In other words, it’s usually better to analyze more artifacts from fewer units than fewer artifacts from more units.
The placement of the hydration rim sample cut. Different artifact surfaces may be created at different periods of time through breakage, rejuvenation, and scavenging. A technological analysis of the artifact to be analyzed may prove to be a useful and productive part of the research strategy. The careful placement of multiple cuts at surfaces of different potential ages, for example, can provide evidence not only of the original manufacturing event but of later periods of reuse.
We hypothesize that stratigraphically, artifacts tend to migrate upwards over time as archaeological deposits accumulate. During site formation activities, some older artifacts will become mixed with contemporary materials, a cycle that will repeat itself throughout the history of the formation of the site. Because of this, the hydration rim values of artifacts from a buried stratum will span not only the range of the deposition of that particular stratum, but all other underlying units as well. Similarly, the artifacts collected in the uppermost deposits (or on the surface) of a site tend to provide a temporal sampling of the entire period of occupation at the site. In practice, we have observed that a carefully collected sample of artifacts from apparently deep and undisturbed deposits will generally show a surprisingly weak relationship between depth and hydration rim width. The hydration analysis of a simple surface collection of artifacts may prove to be an effective and simple way in which to assay the occupational history of the entire underlying site.
Preparation Guidelines
Normally, a single small hydration cut is made for each sample. If you have any special requests regarding the location of measurements on any artifact or would like measurements made at more than one location on the artifact, please attach a separate sheet with a photocopy or tracing of the sample(s) and well-marked hydration measurement locations. It is best not to mark the artifact directly with any type of paint (such as correction fluid) since this may make the hydration rim more difficult to measure . There are no size restrictions for samples submitted only for obsidian hydration analysis, although very small samples may be completely destroyed during slide preparation.
Sample Submission Instructions
To make sure that we get all the information that we need, we provide a sample submission form for this purpose. On request, we’ll also be glad to send you a copy.
What we would like to know about you and your project is:
Your name.
Your organization (if applicable).
The address where you would like the project returned.
How we can contact you if we should have any questions. An e-mail address is particularly useful for this.
A packing list of all artifacts. This will help us spot any missing (or extra) samples during the login of the project.
The location and elevation of the site(s). UTM’s are best and section-township-range works well. Also please include the state, county, and U.S. Geological Survey map (if known) in which the sites are located. All site locations are treated as confidential. This information will be used to verify the accuracy of the source assignments and is also used to help us locate unknown sources.
Sample provenience. When available, the provenience of each sample (sample numbers, unit coordinates, depth, etc.) is used for the reporting of results.
Additional site information is sometimes useful and is always interesting to us in helping to understand your project. If a site record is available, we’d appreciate a copy. And if there’s anything unusual about the site, let us know and we’ll see if this also extends to the obsidian assemblage.
Digital data – if you can submit any of the provenience data as a digital file (spreadsheet is easiest), it will be greatly appreciated.
Any special instructions about reporting needs or billing details (plus a purchase order or project number, if applicable).
And finally, the name and address of the person who receives the final invoice.