TACTITE
Tactites
are a type of skarn. They are multimineralic carbonate rocks
resulting from contact metamorphism (alteration of country rocks by the heat of
an igneous intrusion) and metasomatism (addition of elements to country rocks
from magmatic or hydrothermal fluids).
The tactite shown below is from a classic locality
along the York River near Bancroft, Ontario, Canada. This is a marble
having calcite (whitish-grayish - CaCO3), ferroan spinel (black -
MgAl2O4 with Fe), periclase (MgO), and Mg-Ti borate
minerals.
Tactite
(8.9 cm across) from the York River Skarn (a.k.a. York River Tactite
Zone), eastern side of York River, ~0.3 km north of Highway 28 (Highway 500),
Dungannon Township, Bancroft District, Hastings County, southern Ontario,
southeastern Canada (45¼ 04Õ 08Ó North, 77¼ 43Õ 57Ó West).