Published 2006 in: Geological Society of America Abstracts with Programs 38(4): 17.




ST. JOHN, James M., Department of Geological Sciences, Ohio State University at Newark, Newark, Ohio 43055, USA,

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 “granite” and “marble”.  “Granite” is any relatively hard rock (H = ~6-7) that will take a fine polish.  “Marble” is any relatively soft rock (H = ~3-5) that will take a fine polish.  “Granites” 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).  “Marbles” are typically limestones, marbles, serpentinites, and tectonic breccias.  Samples are easily obtained from waste rock piles at granite-marble companies (“stone graveyards”).  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.



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