Published
2006 in: Geological
Society of America Abstracts with Programs 38(4): 17.
BEYOND DECORATION: THE USE OF COMMERCIAL DECORATIVE
STONES IN GEOSCIENCE EDUCATION
ST. JOHN, James M., Department of Geological Sciences,
Ohio State University at Newark, Newark, Ohio 43055, USA, stjohn.2@osu.edu
Decorative stones are (usually) highly
polished slabs of sheet rock used principally for interior and exterior
decorative purposes, such as facing stone, countertops, and flooring.
Hundreds of varieties have been quarried and sold throughout the world for
centuries. Many currently available decorative stone varieties are
Precambrian, mostly deriving from the Brazilian Shield, the Indian Shield, and
adjacent orogenic belts. The two principal commercial categories of
polished decorative stones are ÒgraniteÓ and ÒmarbleÓ. ÒGraniteÓ is any
relatively hard rock (H = ~6-7) that will take a fine polish. ÒMarbleÓ is
any relatively soft rock (H = ~3-5) that will take a fine polish.
ÒGranitesÓ in the commercial decorative stone trade are typically intrusive
igneous rocks and high-grade to very high-grade metamorphic rocks (e.g.,
granites, granodiorites, porphyritic granites, rapakivi granites, anorthosites,
monzonites, gabbros, norites, gabbronorites, dolerites, gneisses, granulites,
charnockites, migmatites, metaconglomerates). ÒMarblesÓ are typically
limestones, marbles, serpentinites, and tectonic breccias. Samples are
easily obtained from waste rock piles at granite-marble companies (Òstone
graveyardsÓ). Despite the free, abundant, ~durable, and high-quality
nature of decorative stone materials, they are underutilized in geoscience
education. The polished surfaces allow for ready observations of textures
and minerals, unobscured by weathering. They can serve as fantastic
display, lab, and reference specimens for lower-level undergraduate, upper-level
undergraduate, and graduate level geology classes. Because specific
localities, ages, and geologic contexts are readily determined for many
samples, they can also serve as research-grade and museum-grade reference
specimens.