Brief Description: Cryptocrystalline, solid, opaque and shapeless quartz that has either organic (diatoms, radiolarites) or inorganic origin and is found in the form of extended layers in sedimentary rocks. It has glossy to dull lustre and various colours. Lydite (that is mentioned as Lydi by Theophrastus ) comes from river Tmolus of Lydia and is a black, clean, solid, variety of chert that is used in order to define the quantity of gold in various alloys. 
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