Abstract
1., "Oya-ishi" is an important building stone from Oya, Shiroyama-mura, Kawachi-gun, Tochigi Prefecture, Japan., 2., The writer has made studies on its geological and mineralogical properties and their effect on use as building stone., In this preliminary report, the writer describes the geological occurence and properties of "Oya-ishi"., 3., "Oya-ishi" is a Tertiary green tuff containing volcanic rock fragments which are commonly altered to clay minerals and are called "miso"., The thickness is about 3O0m., 4., The writer has classified "Oya-ishi", from the view point of building stone, into three parts: Upper, middle and lower., The upper part is classified into two zones: Upper and lower., The middle part is classified into three zones: Upper, middle and lower., 5., The lower part is easily decomposed by weathering, so it has no value as building stone., Toe middle and upper zones in the middle part are used mainly for building stone., The lower zone in the upper part has the properties required for best-quality building stone., The upper one in the upper part has no value for building stone, because of theinclusion of many large "miso".,
