Petrographic study of pottery samples from the Heping Dao B site (Heping Dao Island, Keelung, Northern Taiwan)

Heping Dao B (HPDB) is an archaeological site located in the small island of Heping Dao, off Keelung, northern coast of Taiwan. The site preserves a very complex and uninterrupted sequence of occupation from the early occupation of Taiwan, in the Neolithic, to the present times. It comprises therefore the prehistory of the island, its transition to the historical period with the European colonization of Taiwan, the Chinese (1668-1895) and Japanese (1895-1945) colonial periods and important remains from WWII, and the postwar colonial occupation by the Kuomintang up to the end of the 20th century. The prehistoric period is particularly complex to unravel due to stratigraphic questions and a traditional focus on ceramic typologies. We aim to overcome these difficulties by providing additional technological information on a sample of ceramics from HPDB.

Optical microscopy is a common method to analyse and characterize the components of pottery. These studies are carried out with thin sections and are able to identify the components and the morphology of the aggregates, and determine the porosity and the different types of clay matrix. Moreover, these studies are useful in order to distinguish the minerals which are formed in paragenesis with the clay from those which were added as temper in order to improve the properties of the pottery.

The assessment of the pottery from Heping Dao B has been carried out by means of eleven thin sections obtained from samples that define specific pottery groups. Every thin section has been studied to identify the components, aggregate size, morphology, voids and textural relationships. According to the initial findings of this study, the predominant component in seven of the analysed samples is quartz, while sandstone is commonly found in three of the thin sections. It is also important to note that sandstone components are remarkably present in three of the seven samples aforementioned. In the remaining sample, other minerals and components, as volcanic stones, feldspars and pyroxenes are present in varying proportions, highlighting the diversity of materials in the studied area. These results provide a valuable insight into the mineralogical composition of the samples and could serve as a starting point for further investigations into their geological origin and possible uses.

Petrographic study. Pottery samples. Archaeological site. Taiwan.