Nile clay is NOT a single petro-fabric. Nile clay is a ubiquitous and readily available clay source throughout Egypt along the Nile Valley and Delta. This ceramic raw material was utilized throughout Egyptian history from the Predynastic to modern times for a range of vessel forms and types. Common especially for utilitarian ceramics such as beer jars, bread moulds, and cooking pots. Fairly easy to identify macroscopically and petrographically through it has some variability. The principal challenge with classifying Nile clay specifically is its ubiquity and similarity over a broad area. Past chemical studies have shown some elemental differences at a large scale of tens of kilometers. There may be petrographic differences as well with minor differences in amounts of inclusions such as mica (muscovite and biotite), feldspars (potassium and plagioclase), quartz, pyroxene, and amphibole. Size differences are sometimes notable, particularly for rock fragments. This may suggest that Lower Egyptian Nile clays could have few rock fragments and heavy minerals (pyroxene/amphibole), while Upper Egyptian Nile clays may have more intact rock fragments and possibly more heavy minerals. However such a supposition has not been tested and it would be difficult to do so.

The petrographic study of Nile clay pastes has instead focused on technological differences between fabrics, e.g., the addition of plant remains, grog, or other materials, as well as variation in the coarseness of inclusions and their frequency. In relation to specific vessel forms, especially cooking pots, it is possible to identify particular paste recipes with technological value. However, in some cases a similar paste will have been utilized for a broad range of vessel shapes. Likewise, general petrographic determinations of firing temperature suggest a common range between 750°C to 850°C. Variation by form for firing temperature occurs in only a few specific cases (i.e., storage containers at lower temperatures, some fine ware at higher temperatures).

In sum, Nile clay wares may be said to contain Nile clay as the paste raw material, but this statement does not offer information about source. (see also ASW-Nile_01, ASW-Nile_03, ASW-Nile_05 in Peloschek 2015)

GENERAL THOUGHTS ON PETROGRAPHY IN EGYPT

Mary Ownby and Lisa Peloschek, two petrographers who have done extensive studies of Egyptian ceramics, describe the issues of determining Egyptian petro-fabrics as follows:

"Within Egyptian ceramic studies, the establishment of the Vienna System in the 1980s allowed for a common terminology to be used for the description of the various raw materials utilized for pottery production. This system divides ceramics generally into those of Nile clay, calcareous Marl clay, mixed clays, Aswan clays, and others (often for material from the oases). Such divisions were based on examination of material mostly from the Middle and New Kingdom, with applications to pottery from other periods limited. Overall, while this system created a general list of clay paste materials, it did not facilitate intersite comparisons or provenance determinations. Today, most ceramists create fabric/paste groups that are site specific and occasionally those are examined petrographically to clarify group divisions and specify raw materials utilized. It should be noted that while ceramists rarely refer to the Vienna System divisions, the terminology has in some instances remained in use. Intersite relationships between petrographically examined materials have been made in a few cases, but by and large has been beyond the scope of research."