Investigation and development of several new materials for high-temperature shields have yielded three reasonably cheap materials which are structurally stable and able to withstand high temperatures and high radiation fields. Calculations indicate good neutron attenuation properties. These materials have undergone extensive development and testing for both physical and radiation effect data. They are (1) serpentine rock, (2) calcium borate, and (3) borated diatomaceous earth. Serpentine rock (3 MgO·SiO2·2H2O), as asbestos mineral, retains its water of hydration to temperatures as high as 950°F. It can be used either dry-packed, or as the aggregate in concrete, with densities attainable of about 130 lb/cu ft. Structurally, the aggregate is not quite as good as concrete. Calcium borate is the commercial name applied to a number of borated calcium minerals pressed into an asbestos matrix to give a boron content of about 12 w/o, with a density of over 70 lb/cu ft. Although the composite is brittle, it can be fabricated into shapes rather easily. Tests indicate it will withstand temperatures up to 1800°F with less than 3% shrinkage, and can be exposed to a neutron irradiation of 2.4 × 1020 nvt without damage. Diatomaceous earth, a porous commercial refractory material, has been successfully borated to the extent of about 2 w/o boron. It can be used as an aggregate in portland or lumnite concrete to give good strength properties and densities of 78–82 lb/cu ft.