Information for archaeologists

The archaeomagnetist will normally require at least half a day to undertake the sampling, make the appropriate notes, etc. The optimum time for both the archaeomagnetist and the archaeologist is usually before the structure is removed or destroyed. However, there are clearly practical problems for both partners in finding such a common time! As such structures are of generally little value, after having been fully recorded, it is common that the archaeomagnetist can effectively assist in destroying the remaining feature (under the supervision of the archaeologist) to expose any underlying features.

However, if the site is to be preserved or reconstructed, then the archaeomagnetist must be advised of this so that the least invasive sampling methods can be used. For example, a brick can be removed to enable samples to be taken from immediately below it, and the brick then replaced to hide the sampling. As a variety of sampling methods are available, this must be discussed with the archaeomagnetist before they arrive at the site!

The samples to be taken should not have been treated with, for example, a preservative and should, as far as practicable, be in their pristine state.

The local site archaeologist will normally be responsible for assessing any hazard during sampling. The archaeomagnetist must obey all instructions of the site archaeologist on this matter. (see Hazard Assessment)

The fundamental requirement is that the object to be dated (let’s say the base of a kiln) should be undisturbed since it was originally fired. The archaeomagnetist usually says that the feature must be “in situ” but this term is much stricter than the conventional archaeological meaning of not being external to the site. It is vital that the kiln, in this example, has not been disturbed or, if tilted because of differential subsidence or kiln-wall fall out/in, etc, or that such motions can be determined to within 1º. (Conversely, archaeomagnetism can be used to distinguish such motions.) This also means that parts of the structure should not have been reconstructed, including the removal and even immediate replacement of, for example, one of the bricks. Please advice the archaeomagnetist of any such suspect areas.

There are few special requirements, but the archaeomagnetist will be primarily interested in the most strongly fired parts of the structure or object for intensity dating and geophysical interpretation. Ideally the material should also be uniform in colour and composition.

Although equipment and instruments are relatively cheap compared with radiometric dating techniques, the actual costs for directional dating is labour intensive and hence similar. Intensity dating has been more automated, but the equipment costs are higher, so that the costs are currently also similar to radiometric methods.
However, there are few commercial companies involved in this method. Most of the laboratories are currently in academic or government agencies. In these cases, some of the running costs may well be born by the agency, in which case the minimum charge could be purely the costs of travel to the site and accommodation if necessary. These can only be established by contacting the nearest available institution (see Archaeomagnetic Laboratories)