An investigation of the silica deposits of southern Illinois . 38 Cone 16 In this v/ork the material with aji index of over that of was calledchert, although part of it v/as quartz and a small amount, silicates of results show that the specific gravity drop is due to the tridyraite forma-tion. Due to the quartz present in the material to the aiuount of about lO/o andto the comparatively short duration of burning the lowest, specific gravity valuethe materials could in this work would be Ov/ing to the short heattrea
An investigation of the silica deposits of southern Illinois . 38 Cone 16 In this v/ork the material with aji index of over that of was calledchert, although part of it v/as quartz and a small amount, silicates of results show that the specific gravity drop is due to the tridyraite forma-tion. Due to the quartz present in the material to the aiuount of about lO/o andto the comparatively short duration of burning the lowest, specific gravity valuethe materials could in this work would be Ov/ing to the short heattreatment very little of the quartz inverted to cristobalite. If the quartzwould invert completely to cristobalite, the minimum specific gravity woiild beclose to By longer heat treatment, to convert the quartz to cristobaliteand then to tridyraite, v/ould only lower the specific gravity to Theseconditions would never be reached for it is practically impossible to cause allthe material to invert. The lov/er results obtained by the microscopic invest-. 36. igation as compared with the theoretical results was partially due to the removalof the finer particles to facilitate the investigation. The crystals of tridy-mite v/ere very small no doubt and the greater portion of the finer materialconsisted of this. The snail size of these and comparative inexperience of theinvestigator is petrographic work did not allov; him to confirm this statementby actual experiment. Summary:- Although these tests were not extensive as desired, they showsome interesting facte. In genend, the gannister v/ould raake a suitable refract-ory, and is being used for retorts and similar refractories at present. Boththe v/hite silica and novaculite fail to give the strength the gannister givesand in this respect are inferior to it, although they both possess a greaterrefractoriness. They might, under different conditions, produce v/are of requis-ite strength, but owing to their high silica content,
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectminesandmineralresou
