Graphite is identified in a particular schist. Which one of the following conclusions is justified? Graphite is identified in a particular schist. Which one of the following conclusions is justified? The schist formed from a quartz-rich, sedimentary limestone. The rock also contains diamonds; both are crystalline forms of the element carbon. The graphite lubricated shearing movements along a fault, causing a schist to form. The pre-metamorphic rock was a shale or mudstone containing organic matter.