Konkresi adalah massa kompak yang keras, terbentuk dari presipitasi semen mineral di dalam rongga-rongga partikel, dan ditemukan di batuan sedimen atau tanah. Konkresi berbentuk seperti telur ataupun bulat, namun bentuk-bentuk iregular juga sering terjadi. Istilah 'Konkresi' berasal dari bahasa latin Con yang artinya 'bersama' dan crescere yang artinya 'tumbuh'. Konkresi-Konkresi terbentuk di perlapisan strata sedimen yang telah terendapkan terlebih dahulu. Mereka biasanya terbentuk lebih awal ketika terjadi penumpukkan sedimen, sebelum kemudian sedimen tersebut mengeras menjadi batuan. Semen Konkresi ini sering menyebabkan Konkresi lebih keras dan lebih tahan terhadap pelapukan dibanding perlapisan induknya. Ada perbedaan penting antara Konkresi dan nodula. Konkresi terbentuk dari presipitasi mineral di sekitar sejenis nukleus sedangkan nodula adalah tubuh yang tergantikan. Deskripsi yang telah dilakukan semenjak abad ke-18 membuktikan bahwa Konkresi telah menarik perhatian ilmuan sejak masa lalu. Hal itu disebabkan adanya variasi bentuk yang tidak biasa, ukuran dan komposisi, yang membuatnya sempat dikira telur dinosaurus, hewan, dan fosil tumbuhan, hingga puing antariksa atau artefak manusia.

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Referensi

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Pranala luar

Dietrich, R.V., 2002, Carbonate Concretions--A Bibliography, The Wayback Machine. and PDF file of Carbonate Concretions--A Bibliography Diarsipkan 2014-12-17 di Wayback Machine., CMU Online Digital Object Repository, Central Michigan University, Mount Pleasant, Michigan. Biek, B., 2002, Concretions and Nodules in North Dakota North Dakota Geological Survey, Bismarck, North Dakota. Epoch Times Staff, 2007, Mysterious Huge Stone Eggs Discovered in Hunan Province Epoch Times International. Photographs of large cannonball concretions recently found in Hunan Province, China. Everhart, M., 2004, A Field Guide to Fossils of the Smoky Hill ChalkPart 5: Coprolites, Pearls, Fossilized Wood and other Remains Part of the Oceans of Kansas web site. Hansen, M.C., 1994, Ohio Shale Concretions PDF version, 270 KB Diarsipkan 2008-12-16 di Wayback Machine. Ohio Division of Geological Survey GeoFacts n. 4, pp. 1–2. Hanson, W.D., and J.M. Howard, 2005, Spherical Boulders in North-Central Arkansas PDF version, 2.8 MB Diarsipkan 2010-05-27 di Wayback Machine. Arkansas Geological Commission Miscellaneous Publication n. 22, pp. 1–23. Heinrich, P.V., 2007, The Giant Concretions of Rock City Kansas PDF version, 836 KB Diarsipkan 2016-10-20 di Wayback Machine. BackBender's Gazette. vol. 38, no. 8, pp. 6–12. Hokianga Tourism Association, nd, Koutu Boulders ANY ONE FOR A GAME OF BOWLS? and Koutu Boulders, Hokianga Harbour, Northland, New Zealand Diarsipkan 2008-10-14 di Wayback Machine. High-quality pictures of cannonball concretions. Irna, 2006, All that nature can never do, part IV: stone spheres Diarsipkan 2016-03-03 di Wayback Machine. Irna, 2007a, Stone balls: in France too! Diarsipkan 2015-07-13 di Wayback Machine. Irna, 2007b, Stone balls in Slowakia, Czech Republic and Poland Diarsipkan 2008-03-15 di Wayback Machine. Katz, B., 1998, Concretions Digital West Media, Inc. Kuban, Glen J., 2006-2008. Nevada Shoe Prints? McCollum, A., nd, Sand Concretions from Imperial Valley, a collection of articles maintained by an American artist. Mozley, P.S., Concretions, bombs, and groundwater, on-line version of an overview paper originally published by the New Mexico Bureau of Geology and Mineral Resources. United States Geological Survey, nd, Cannonball concretion Diarsipkan 2014-10-15 di Wayback Machine. University of Utah, 2004, Earth Has 'Blueberries' Like Mars 'Moqui Marbles' Formed in Groundwater in Utah's National Parks Diarsipkan 2015-08-02 di Wayback Machine. press release about iron oxide and Martian concretions