NETTUNO fabric 6

NET I.eh.vps(1-4).c, (large) FeMn nodules / (hardness+)

Description on basis of macroscopical observation up to x30 (see image of fresh cross section above and table below)

The fabric is characterized by a reddish colour, with emphasis on Munsell colour 2.5 YR 3/3 (dusky red). A low total volume of inclusions with a modest predominance of black Augite and yellowish white, powdery Leucite is well detectable by eye. Occasionally Ferro Manganese nodules can be seen. The inclusions are angular to rounded and unevenly distributed throughout the clay matrix and very poorly sorted in size. Mica seems present substantially in the smoothened surface but is hardly present in the fresh cross section. When the vessel was shaped, the mica flakes in the clay tended to become orientated along the surface plane. As with the previous fabric, the sherds crumble, though only on surface areas, not on fresh cross-sections. In fresh cross-sections the ceramic appears somewhat harder compared to average 2-3 on Mohs’ scale.

table 13.1    properties of NETTUNO fabric 6 in a fresh cross section (x: absent / p: present)

The fabric in general gives the impression of a low percentage of inclusions, though some large to very large Ferro-Manganese nodules can easily be detected, even by naked eye. The total volume of inclusions is between 5 and 10%. The Ferro-Manganese nodules are 1-6 millimeters in size and possess a concentric structure. Inclusions are found within them.

The clay matrix seems insufficiently blended or even hardly prepared, with lighter and darker zones and fine fissures in variable directions. Besides Ferro-Manganese nodules, mainly Augite and Leucite are present, that may be (partially) weathered. Inclusions vary in shape from euhedral to abraded and rounded. As in fabric number 5, the Leucite present is recognized better in sections. At the proper thickness of 30 micron the (partial) weathering erases the already hardly detectable complex twinning under crossed polars. The weathering of Leucite at grain bounderies is visible as a cloudy structure under plain polarizors light, very much resembling what is found in thin-sections from Tuff stone at Satricum. Most of the inclusions seem to show several stages of weathering. The areas in full transition are isotropic while some not fully tranformed areas show traces of twinning considered characteristic for Leucite. However, Delvigne mentions: “This pattern of twinning, related to a phase transition during cooling, may be considered a characteristic of leucite crystals, although it is observed also in some crystals of garnet”. (Delvigne, 1998: p. 15). None of the weathered inclusions possesses a high relief though, which is an essential characteristic of Garnet (Gribble & Hall, 1992: pp. 87–88; MacKenzie & Guilford, 1980: p. 8). Besides this, the sporadically detected Garnet in this section shows no traces of weathering, is more brownish yellow under plain polarized light and clearly isotropic under crossed polarizors. Therefore the ((partially) weathered) inclusions are considered to be Leucite. In the fresh cross-section of sherds this Leucite is detectable as partially milky white particles with clear white (occasionally powdery) opaque areas.

The clay matrix with traces of insufficient blending, the relatively large Ferro-Manganese nodules, and fissures in varying directions, indicate that the vessels of this fabric were modelled by hand only.
 

table 13.2     properties of NETTUNO fabric 6 in thin section (x: absent / p: present)