Minerals (Silicates). Deposits. Mineral Index

The volume is entirely devoted to the natural occurence of thorium minerals. The main part describes the 29 known silicates of thorium and covers in detail the following topics: - occurence, especially the paragenesis and processes of formation; - chemistry, with complete analyses and discussion of formula and isomorphic replacement, especially in relation to the processes of formation; - crystal form and structure; - physical properties, especially the optical properties; - chemical and thermal behavior. It soon becomes obvious that the chemical formulas of the thorium silicates are not as simple as usually given in textbooks. Structurally, the nesosilicates predominate with 9 specimens. There are 4 sorosilicates, 5 cyclosilicates, and 11 unclassified specimens. The second part is an overview on deposits of thorium comprising classification and types of deposits, a short description of individual deposits (arranged by continent and country), and some data on resources, availability, production, and prices. There are only a few deposits that are capable of being exploited for thorium as the main product, whereas by-product thorium can be obtained from a number of deposits, especially those worked for rare earth elements and/or uranium.