The instant invention is concerned with the production of glass bodies which, after being hydrothermally crystallized, exhibit a relatively high degree of machinability and good chemical durability. Such bodies are produced by hydrating glass particles having compositions within a very narrow interval of the Na.sub.2 O--Al.sub.2 O.sub.3 --MgO--SiO.sub.2 field. The hydration simultaneously results in the development of quartz crystals and causes the glass particles to sinter together into an integrated solid body which can be readily shaped and drilled by hand and machine tools. Upon firing to remove the water in the glass structure, a porous body is produced that will exhibit no more than 10% linear shrinkage and, most preferably, less than 5%.

The present invention is concerned with the preparation of hydraulic cements, demonstrating high mechanical strength, long term resistance to attack by moisture, and virtual freedom from creep, from glass powders consisting essentially, expressed in terms of mole percent on the oxide basis, of about 60-76% SiO.sub.2, 15-30% K.sub.2 O, and 2-15% total of at least one metal oxide selected from the group of 0-10% Al.sub.2 O.sub.3, 0-5% V.sub.2 O.sub.5, 0-5% TiO.sub.2, 0-5% MoO.sub.3 and 0-5% WO.sub.3. The cements exhibit particular utility in forming strong cellular ceramic articles. The glass powders may contain a phosphate component in which case the composition ranges are limited to 68-76% SiO.sub.2, 18-24% K.sub.2 O, 2-4.5% P.sub.2 O.sub.5 with the molar ratio K.sub.2 O:P.sub.2 O.sub.5 ranging between 5 and 10, and 2-5% total of at least one metal oxide selected from the group of Al.sub.2 O.sub.3, MoO.sub.3, V.sub.2 O.sub.5 and WO.sub.3.

A fertilizer from which potassium is released slowly comprises a frit produced from a potassium/silicon composition in the range K.sub.2 O.2SiO.sub.2 to K.sub.2 O.4SiO.sub.2 and containing from 5.5% to less than 10% by weight of calcium oxide.

Abrasion resistant glass, which consists essentially of the following components: provided that R is at least one member selected from Mg and Ca, and R' is at least one member selected from Li, Na and K, and of which the density measured at room temperature is at most 2.43 g/cc.

Abrasion resistant glass, which consists essentially of the following components: provided that R is at least one member selected from Mg and Ca, and R' is at least one member selected from Li, Na and K, and of which the density measured at room temperature is at most 2.41 g/cc.