|Granite landscape, Halibut Point|
|Folly Cove pier,|
the shipment point for Halibut Point granite a century ago
Chemically similar blends of magma that cool and petrify more quickly will not develop the combination of strength and grain that characterizes granite. Compare it to the finer-textured rock below, which may have been brought from afar by a glacier, or eroded from a relatively quick-cooled intrusion within the bedrock.
|An exotic boulder on the Halibut Point shoreline|
Feldspar silicates make up much of the mass of granite as well as shaping its particular 'behavior.' It's the lighter-colored substance in the photo. It may take on pink, gray or brown tints according to its chemical individuality and lend specific characteristics to the stone.
All granites are felsic, relatively rich in elements that form feldspar and quartz: silicon, oxygen, aluminum, sodium, and potassium. Granites can be contrasted with mafic rocks, which are relatively richer in magnesium and iron (ferric). Incorporating denser metals that predominate in the earth's core, mafic rocks such as basalt are heavier than granite. Felsic rocks tend to 'float' above them in the earth's crust, forming the continents.
Granite begins as a monolithic formation far below the earth surface. Cracks and seams develop as conditions change. Incomprehensible pressures increase during tectonic collisions. Conversely pressures decrease when the stone is relieved of miles-thick overburden through millions of years of erosion. The accompanying expansions, contractions, and shifts are expressed in the pattern of joints. According to their placement the joints make the stone more or less desirable for quarrying.
All granite is not equal. The cakey-looking Chelmsford granite utilized these days for curbstones on our Cape Ann streets - cheaper to saw and split - disintegrates at the first rap of a snowplow.
Mastering the challenges and employing the qualities of Cape Ann granite imparts a satisfaction to tradesmen and sculptors, as well as integrating their artisanship to the native terrain with a cohesion for all to enjoy. Nature's vernacular engenders our own.