I would have thought it would be very difficult to do in a meaningful way. There are depositional differences, mineral content differences even within formations, textural differences within formations, and using (British) flint as an example, between each band. You could end up with so many sub-divisions that it would be impractical to use. Just a thought

Thanks Paul for your reply, I agree with you. Finding a unified nomenclature is difficult. Moreover, it is difficult between archaeologists and geologists of the same language. However, I think that it is not impossible to apply strict criteria for a classification adapted to local microfacies. As you said, differences can exist within the same geological formation, this may be related to the flint genesis conditions. Conversely, I have distinguished various siliceous microfacies, defining regional varieties, after associating several criteria (macroscopic, microscopic and geochemical criteria (see my publication in Internet archeology).

All the best.

I do agree with you there may be potential, but if you look at this publication 'Scandinavian Flint: An Archaeological Perspective', ISBN: 9788779342781 (if you have not seen it already) you will see the difficulties that might arise. Distinguishing between the flint types can become subjective because of very local differences, yet different areas might look very similar. I hope you are successful if you try, but perhaps very local criteria may be easier than on a broader geographical scale.

You are right. Indeed, it depends on the studied samples, and it is very rare that we find certain flint varieties with trace elements which allow to to assign them to a specific geological stage. in any case, thank you for your answers..

Does the "An Archaeological Perspective', ISBN: 9788779342781 " exists on PDF file? I will be grateful to you or anyone who can provide to me this reference.

I am afraid I have only ever seen it in hard copy. There are some excellent photographs of the flints from across the region to illustrate the variations. Good luck accessing a copy.

I thank you very much for your reply anyway.

What about applying a strictly mineralogical criteria? Enough XRD (etc.) has been done on classified specimens from elsewhere, that this might be useful?

Hi Alison, There are hundreds of references in the world, if not more, for the characterization of different siliceous rocks. There is evidence that the combination of macroscopic (color, zonation, texture, opacity, grain and inclusions ..), petrographic (by study of thin sections), micropaleontological and geochemical (XRD and neutron activation analysis) analyses is essential for the discrimination of siliceous microfacies.

For the samples that I examined, the results were reported on a little regional scale. The results obtained from petrographic analysis confirm the existence of a wide range of microfacies. This evidence suggests that the silica precipitation conditions were neither uniform nor homogeneous, and occurred on various original matrices (such as deep marine environment belonging to the Middle Lias  and beach environment of the Upper Lias). The DRX analysis showed that one sample has a higher ratio of dolomite with very small amount of calcite then the other samples, ..). Further investigation by ICP/MS (Inductively Coupled Plasma Mass Spectrometry) should be undertaken to determine trace elements.

Of course, these results are only valid for flint varieties I studied, then it is possible that for researchers studying flint from other regions, these analyses might not have the same impact on the flint discrimination . These analyses are expensive, that’s why it is important to establish regional lithothèques containing prototypes reference discriminated by all of these analyses to serve as reference for further comparisons. Many lithothèques are very successful as in Romania, France, ...

Food for thought: not only siliceous rocks are of interest.

Archaeological and geological classifications for raw materials are not necessarily the same, because different questions are being asked. Archaeologists are interested in human choices of raw materials, and in how those are treated by humans. Geologists are interested in how Nature formed, changed, and/eor emplaced the materials. Archaeologists are interested in such aspects as colour, primary form, flaking properties, which are not often of major concern to geologists. It is useful for an archaeologist to find out how a geologist would classify a given rock, but that should not constrain the archaeological terminology. It can be important to know, however: I have recently seen 'orthoquartzite' designated by an archaelogist as (vein) 'quartz'. In that case, the two materials have very different properties of interest to archaeologists, and calling quartzite 'quartz' is misleading. There can also be a problem in that geologists may change their minds about how to classify a given rock type based on newer information about its origin; the archaeological properties of interest don't change, however.

Dear all,

My apologies, I haven't mentioned in my question that the matter deals with the knapped siliceous rocks such as flint, chert, chalcedony, ...

I agree with Maxine Kleindienst, when she said that the archaeologist is more interested by aspects related to the choice of raw material varieties regarding to their quality and their exploitation by prehistoric populations. However, I still believe that the use of a common terminology between geologists and archaeologists in a given region should be encouraged, as it allows local and territorial definition of siliceous groups to answer the question of raw material mobility. Then it will be the turn of the archaeologist to find the behavioral aspects of prehistoric populations regarding to these exploited siliceous rocks.

You are correct in citing the example of orthoquartzite (although it is considered as a sandstone by some authors) to raise the issue of the difficulty of finding a common nomenclature.

I hope you'll find in this paper some of interest (see the link below).

All the best.

http://archives.datapages.com/data/meta/sepm/journals/v42-46/data/044/044001/pdfs/0264_firstpage.pdf

Thanks for the paper. I was referring to the Naibor Soit outcrops in the Olduvai Gorge area, which are in fact, a highly metamorphosed quartzite. There are also quartz veins in the metamorphic rocks,. Geologists discriminated between the rock types, but interestingly, some archaeologists have called them both 'quartz' although the flaking properties are very different. The master stone workers beginning in the Acheulian could use them both.

Maybe a regional case study would be of general interest? When I started fieldwork in the Dakhleh and Kharga oases of Egypt's Western Desert in 1986, with I. A. Brookes, we agreed to call the siliceous rocks used for artefacts 'chert', except for obvious chalcedony that could be identified in hand specimen. That was to avoid the problematic differentiations of 'flint' vs. 'chert' already in the literature. Later, other geologists agreed with that usage for both disciplines. At Dakhleh, only two formations carry chert, mostly in nodular form; the upper Cretaceous Mut Fm.(Qusier Group) mudstones, and the Paleocene Tarawan Fm. limestones. Unfortunately, without cortex, they are difficult to accurately distinguish in hand specimen. Later, we found that the chalcedony could derive either from fossil Pleistocene spring vents, or from large nodules (geodes) in the Mut Fm. No one has found it worthwhile to do compositional analyses. Secondary sources are widespread.

The situation at Kharga is far more complicated; sources range from the upper Cretaceous in the Lowland to the Eocene limestones capping the eastern Plateau. We can roughly source some major chert 'types' along the Escarpment and Plateau edges, but not the high degree of variation seen in artefacts. The 'cherts' are highly variable in friability, fracture patterns, colour, texture, and visible composition. Some are fossiliferous. They occur as large and small nodules, but also in thin sheets (tabular). The Kharga Oasis Prehistory Project does not have the resources for a years' long study of outcrops, but if anyone wishes to undertake that, I am sure it would be a fascinating study that could be tied to different human uses of lithic raw materials through time, as well as to the geology.

Thank you very much Maxine Kleindienst for this valuable information. It is true that epigenetic problems occurring after flint diagenesis complicate greatly flint outcrops research,

Not if most geologists I have spoken to are any indication...

Rather than strict criteria for objectively determining the "type" of silicious rock, perhaps the best approach is to define them based upon their "human relevant" characteristics. If it looks like basalt, works like basalt, has similar hardness to basalt, same edge properties, etc. etc... then does it really matter that it is technically some other form of fine-grained volcanic? As far as ancient people were concerned, the western science mineralogical standards mattered not a mustard seed. This is an important conversation, however, since it gets at the heart of whether abstract, "objective" definitions are more important than the subjective "experiential" categories of the people who created the archaeological record?

Even if the questions that are being asked may pertain to different characteristics of the natural material, it is important that natural materials are referenced in publications in a way that communicates the fundamental properties of that material, otherwise readers may misunderstand the significance of the materials studied or the questions being asked.  Mineralogy and lithology are two simple ways to identify materials; It also provides a way to link the archaeological study to regional studies of geology.

As an example with which I am personally familiar, referring to artifacts that are green hard stones all by the name of "jade" is misleading, even if many different lithologies are found to be in use in the same way that "true" jadeite-jade is used. Even if the archaeological or cultural use of green stones are considered similar to the use of jadeite jade, many green stones have vastly different material properties that will alter the complexity of the manufacturing process, the functionality of the final product, and the quality of that product. It will also alter how accessible the parent material is, which may cause the researcher to wonder about geologic sources and extraction techniques. Thus, the mineralogy and/or lithology may influence archaeological interpretations, and knowing this information at the onset of a study is valuable to both researcher and reader. 

For this reason, it should be important to researchers from diverse disciplines that study the same types of materials, albeit with different questions in mind, to utilize a common nomenclature; for example, identification of mineralogy and/or lithology is a basic and straightforward way to clarify many material properties of your artifact. Perhaps in the case of cryptocrystalline polymorphs of quartz, like chert versus chalcedony, the geologic vocabulary may not give much more information for asking archaeological questions. However, it will help clarify characteristics of the material for your readers, for example, which material is easier to manipulate or which is more durable. Furthermore, if you are interested in any provenance study of the artifacts, one cannot approach these questions without identifying the geologic origin of the material. 

although geologists may not ask the same questions, I would encourage collaborative efforts between archaeologists and geologists in order to identify materials according to one terminology. The researcher only has something to gain from making the research material more accessible to a wider audience.  

There is a paper, written by a Czech geologist who has been collaborating with archaeologists for many years that might be of interest: A. Přichystal, Classification of lithic raw materials used for prehistoric chipped artefacts in general and siliceous sediments (silicites) in particular: the Czech proposal. Archeometriai Műhely 7/3, 2010, 177–181. It can be found online here:

http://www.ace.hu/am/2010_3/AM-10-03-AP.pdf