GLEANING SCIENCE FROM A “GRANITE” KITCHEN COUNTERTOP

We remodeled our kitchen in 2019 and for countertops we fortunately chose a “granite” that actually is a diamictite (commercial name “Fusion quartzite,” from Brazil). It contains clasts ranging in diameter from 0.5 m (1.5 ft) to a few mm (< 1 in) in a matrix of fine-grained clastic. Clasts consist mostly of dolostone and limestone, ranging from gray to tan, occasionally with one carbonate texture replacing another, rare metamorphic or volcanic clasts, and black organic-rich metasiltstone. Many carbonate clasts preserve original bedding. The components of this rock are mildly recrystallized around the 350° C threshold for quartz plasticity, have undergone incipient transposition, and precipitated vein quartz. The rock mass was deformed primarily by pressure dissolution producing brownish-gray pressure-dissolution layering in the finer-grained components, attesting to the low temperature of deformation. Quartz veins were deposited in zones where compressional deformation was resolved into tension cracks. They contain mm-size grains of magnetite and prismatic red hematite(?). Small clasts were rotated forming dextral shear-sense indicators with tails of carbonate or pressure-dissolution selvages. Incipient transposition is preserved by interdigitation with the matrix parallel to pressure-dissolution selvages at the ends of several carbonate or black metasiltstone clasts. A simple shear component was clearly part of the deformation plan of this rock mass.

We eat most of our meals on our island countertop, and each time, something new ”appears” for a careful eye to observe. I strongly recommend that geologists and others interested in earth history select their countertop materials with care to have many years of interesting scientific inquiry as you and your families enjoy eating their meals.