The foreign sliced rock or 'F' collection consists of about 10, 000 specimens and thin sections, cited by their 'F' numbers. These include material archived from recent overseas projects and much collected during the late 19th or early 20th Century from regions within what was then the British Empire. It also includes 'exotic' materials donated to the Survey in its earlier years. Its coverage varies, although there is a predominance of African material. It is indexed on paper registers, and approximately 20% has been input onto 'Britrocks'.
