Sentence:  Do you enjoy the amber glow seen through the <WSD>isinglass</WSD> window of a wood stove? ... "Muscovite" (colorless, white, or pale red or green) mica is also commonnb...; it was named for "Moskva" (Moscow), where much of Europe's mica was mined. <WSD>Isinglass</WSD>, mentioned above, consists of thin, transparent sheets of muscovite. 
Meaning of the word marked with <WSD> tags:  A thin, transparent sheet of mica (probably from its similarity to true isinglass).