• this is an igneous rock
• the porphyry from this area has a distinctive appearance and is known as Banockburn Porphyry because it is found in Bannockburn Township, Ontario
• it has also been called Matachewan Porhyry
• the porhyry has pink & cream rectangular feldspar phenocrysts  distributed in a dark gray, brown or black country rock
• it has a porphyritic texture (angular grains) in trachyte pophyry
• Trachyte: Trachyte is the fine-grained extrusive equivalent of syenite and is found in volcanic flows
  source: Rocks and Minerals of Ontario, Geological Circular 13, Ontario Department of Mines and Northern Affairs, 1972 p.58
• a large specimen can be seen in the Peter Russel Rock Garden at the University of Waterloo http://earth.uwaterloo.ca/outreach/rock-garden/matachewan-porphyry

Reference: Rocks and Minerals for the Collector, Cobalt - Belleterre - Timmins, Ontario and Quebec  2000, p.113 - 115