Four sepiolite deposits of different origin, which occur near Las Vegas, Nevada, are compared and described. They include a playa deposit, a valley terrace deposit, and two types of vein deposits. The physical and chemical characteristics of the four materials are described, the engineering and commercial features are considered, and the varied origins of the sepiolite are discussed. X-ray powder diffraction data, infrared spectra, thermal characteristics, and chemical analyses are given for the Two Crows sepiolite. The vein deposit is proposed for use as a clay mineral reference standard because of its purity and availability. The apparent diverse morphology of the sepiolite deposits is shown with its common, lathlike basic structure.

With an incidence of less than 0.3 per cent, post-radiation sarcomas are rare malignant neoplasms with a very poor prognosis. On average, they occur after a latency period of at least 15 years following radiation therapy with doses ranging from 24 to 80 Gy. We present the case of a post-irradiation malignant fibrous histiocytoma (MFH) on the floor of the mouth in a 79-year-old male patient arising only five and a half years after radiation therapy. The primary tumour was classified as a well differentiated squamous cell carcinoma of the right rim of the tongue. Primary therapy was surgical resection of the tumour and post-operative radiation with 50 Gy. Five and a half years later, the patient developed a rapidly progressing MFH within the field of radiation.

A case of malignant fibrous histiocytoma, which developed in the tongue of a 16-year-old girl is presented. Surgical excision with, or without, radical neck dissection is the treatment of choice of this type of lesion.

The giant cell variant of malignant fibrous histiocytoma is a rare entity in head and neck. Only eight well documented cases of this type are reported in the English literature. These tumours affect the superficial and deep structures of the neck most often and are best treated with prompt radical surgery. The prognosis of the giant cell type of malignant fibrous histiocytoma is dependent on the location of the tumour, with superficial tumours having a much better outlook.