Identification of Alumino-Silicate Polymorphs, Using Field Spec®3, in Hamadan Region

Study of alumino-silicate such as andalusite, sillimanite and kyanite are very important in terms of economic condition. In order to study the spectrum of these polymorphs, the Alvand area in Hamedan region and silicate veins of alumino-silicate are selected. For this reason, after the field studies and petrographic of selected samples, spectroscopy analysis was performed by Field Spec® 3 device. Classification and data analysis of samples have been done based on this result. Accordingly, alumino-silicate polymorphs with same chemical composition have similar absorption bands but have different absorption depth in absorption bands in the infrared range and among their other differences are the rates of reflectance. Considering that each one of these three polymorphs forms in differentconditions of temperature and pressure, and each of them has a special physical structure, the difference of rate reflectance of polymorphs are direct relationships with the physical structure of these polymorphs. In this regard, reflects amount of the sillimanite more than kyanite and kyanit reflection is more than from andalusite. In addition, the amount of absorption depth in three polymorphs in their absorption bands were studied and showed that the amount of kyanite absorption´s depth is less than sillimanite and andalusite and amount of absorption´s depth of andalusite only in 950 and 1404 nm is less than sillimanite. According to the conducted studies, reason of absorption bands in each three polymorphs is the presence of certain elements and compounds in their mineralogical composition. At the end, to check the possibility of separation of the desired objectives, the representative spectrum simulated with Hyperion hyperspectral sensors and Aster multispectral sensor.