1985 Volume 93 Issue 1082 Pages 622-628
The andalusite crystals are generally found as a minor constituent of heavy minerals in quartz sands which are used as the raw materials for bottle glasses. The properties of andalusite crystals depend on the types of quartz sand deposits. Although this variation notably influences the occurring rate of andalusite glass stones, yet some amount of the stones is still commonly found in bottle glasses. The andalusite glass stones for the experiment are collected from the significant numbers (1200 pieces) of glass stones present in various kinds of bottle glasses. The reaction of andalusite crystals in molten glass is studied by using a single andalusite crystal and cullets of bottle glass. Thin sections are made from the reacted samples and glass stones. The optical analysis, EPMA and X-ray diffraction are used to observe the reaction zones and to identify the constituent minerals. The reaction zones, found in all of the andalusite crystals are divided into two forms; the first consists only of fibrous aggregation of mullite crystals and the other contains peritic aggregation of needle corundum crystals which grow on the mullite aggregates. The rate constant of andalusite decomposition has been calculated from the data of reaction test. The apparent activation energy, based on the velocity of andalusite decomposition is calculated to be 128kcal/mol. The behaviour of andalusite crystals in a tank furnace is considered from the structure of reaction zone of andalusite crystals, rate constant of decomposition and working condition of the furnace. Most of the andalusite crystals, found in glass stones seem to be decomposed by passing through the zone of moderate temperature which is considered between 1300° and 1350°C.
