Graphite Is Identified in a Particular Schist

Multiple Choice

Graphite is identified in a particular schist.Which one of the following conclusions is justified?

A) The rock also contains diamonds; both are crystalline forms of the element carbon.
B) The schist formed from a quartz-rich, sedimentary limestone.
C) The graphite lubricated shearing movements along a fault, causing a schist to form.
D) The pre-metamorphic rock was a shale or mudstone containing organic matter.