Limestone—a sedimentary rock, chiefly composed of calcium carbonate; formed from the shells of marine animals Marble—a metamorphic rock, chiefly composed of calcium carbonate Metamorphic—changed; usually by heat or pressure to a different form but the same composition Mica—a silicate mineral that forms sheets or layers and contains aluminum, hydroxyl, and alkali ions: K₂Al₄Si₆Al₂O₂₀(OH,F)₄, K₂(Mg,Fe)₆Si₆Al₂O₂₀(OH,F)₄ Mineral—a naturally occurring inorganic substance with an ordered structure; rocks are made of one or more minerals Portico—a porch, with a roof supported by columns Pyrite—a mineral (“fool’s gold”) composed of iron sulfide: FeS₂ Pyroxene—a silicate mineral containing two metal oxides: CaMgSi₂O₆, CaFeSi₂O₆, (Mg,Fe)SiO₃ Quartz—a mineral composed of silicon dioxide, or silica: SiO₂ Sandstone—a sedimentary rock composed chiefly of quartz grains Sedimentary—formed from particles that were transported by water or wind and deposited in layers Volute—a scroll-like ornament on an Ionic column capital Further Reading Acid rain: The facts, 1988: available from Inquiry Centre, Environment Canada, Ottawa, Ontario, Canada K1A 0H3. Amoroso, G.G., and Fassina, V., 1983, Stone decay and conservation: New York, Elsevier, 453 p. Hannibal, J.T., and Park, L.E., 1992, A guide to selected sources of information on stone used for buildings, monuments, and works of art: Journal of Geological Education, v. 40, p. 12-24. Pickering, R.J., 1987, Acid rain: U.S. Geological Survey Open-File Report 87-399. U.S. Geological Survey, Building stones of our Nation’s Capital: Reston, Va., U.S. Geological Survey general-interest publication. Winkler, E.M., 1973, Stone: Properties, durability in man’s environment: New York, Springer-Verlag, 230 p. [Illustration: Limestone] [Illustration: Marble] [Illustration: Sandstone] [Illustration: Granite] Photographs by the author · Edited by Kathleen Gohn · Publication design by Elizabeth Junek ★ U.S. Government Printing Office: 1995-394-904 What Type of Rock is It? Look at the overall appearance of the stone in the building. Observe the color, texture, and structure of the stone. Does the stone look evenly colored, with an even texture? YES ⇒ Look at the grains up close. Do you see fossil fragments (bits of shells or skeletons)? YES ⇒ LIMESTONE NO ⇒ Are the grains rounded, like sand on the beach? YES ⇒ SANDSTONE NO ⇒ {same as next line} NO ⇒ Do you see streaks or clouds of color in a mostly white stone? YES ⇒ MARBLE NO ⇒ Look at the grains up close. Do you see a mixture of colors (black, white, gray, maybe pink or red)? YES ⇒ GRANITE NO ⇒ MARBLE Some of these stones may have layers that were the original beds that formed the stones. [Illustration: LIMESTONE] [Illustration: SANDSTONE]