Short answers, pulled from the story.
Gneiss is a common high-grade metamorphic rock that forms under temperatures exceeding 300 degrees Celsius and pressures ranging from 2 to 15 kbar. Extreme shearing force stretches original rock material into sheets while nonhydrostatic stress develops perpendicular to the direction of greatest compression.
The Acasta Gneiss exists on an island about 16 kilometers north of Yellowknife in Northwest Territories Canada and dates between 3.58 to 4.031 billion years ago. The Sete Voltas gneiss from Bahia Brazil represents the oldest rock outcropping in South American crust at 3.4 billion years old.
Orthogneiss designates a gneiss derived from an igneous rock source while paragneiss originates from sedimentary rock instead. Specific classifications include garnet gneiss which contains garnet minerals and biotite gneiss which includes biotite mica in its composition.
The word gneiss entered English usage at least by year 1757 according to historical records found on page 308 mentioning black vein-stone or rock usually called kneiss. German speakers borrowed the term from Middle High German noun meaning spark because the rock glitters during work.
Facoidal gneiss serves as building material extensively used throughout Rio de Janeiro Brazil for construction projects utilizing gneiss as aggregate for asphalt pavement roads and infrastructure. Transportation networks rely heavily on crushed gneiss mixed with bitumen for highway surfaces while municipalities choose this stone for monuments and foundations due to longevity.