Cherty

Rudely shaped, of hard cherty rock, flat on the inner face, convex on the back. 2759.

Its mineralogical constitution is not simple; in some parts the rock is of a cherty, in others of a feldspathic nature, including thin veins of serpentine.

It is represented by a phosphate-dolostone sequence in Wengan, where it is 33 to 55 m thick and consists mainly of dark phosphate, cherty phosphate, chert, and gray dolomite.