gems, turquoise, turquoise identification

A microscopic study by Hugo Bücking of turquoise from several localities, including Sinai, Nishapur, Steine in Silesia and Oelsnitz in Saxony. Bücking examined thin sections under the microscope and showed that turquoise, although macroscopically apparently amorphous, consists of extremely fine doubly refracting particles or short fibrous aggregates. He compares the microscopic structure of specimens from the different sources and also records changes in color produced by heating. The paper is an important early contribution to the petrographic and gemological study of turquoise, demonstrating that microscopic examination could reveal an internal structure not evident from ordinary visual inspection.