Click on a letter to display a list of all agate names beginning with that letter.


Or, search by text

2851 Uberaba Agate, Brazil,... up to 10 pounds each, some carnelian, ...some have banding, adv., Riviera Lapidary Center, Lapidary Journal, v. 38, no. 12, p. 1561.
2852 Umbu Agate, Brazil, a translucent, gray agate suitable for dyeing, from southern Brazil. Mattos (1974, p. 4) recorded Umbu as a colorless or faintly colored agate found only in Rio Grande do Sul, Brazil, found near Salto do Jacui on Rio Jacqui. That it is probably a colorless agate is supported by being the lowest priced item ($85.00/220 lb. kilo box) supports the above observation. adv., Rocky Joe's, Rock & Gem, v. 2, no. 4, p. 25
2853 Union Road (Agates, Geodes), Missouri, for Union Road, St. Louis County, Missouri. See Barnes, P., 1968. St. Louis County Union Road Agate and Geodes, Earth Science, v. 21, no. 1, p. 42.
2854 Union Road Agates, St. Louis, Missouri. These nodules and geodes were formed during the Mississippian Period about 350 million years ago. They were formed under sedimentary conditions. The agate is a form of quartz called chalcedony. The matrix surrounding some agates is chert. They were first found near Union road (Therefore the name) when Highway 55 was being built in south St. Louis county. They are found in a limited area of about 2 miles centered from the intersection of Highway 55 and Lindberg Blvd. This area is now nearly built up with shopping centers and subdivisions. From an anonymous note that accompanied these agates being offered for sale or trade at the 1995 Greater Kansas City Gem and Mineral Show. Ozment (1966, p. 106-197) and Smith (1976, p. 2264-2267) stated these agates came from the Saint Louis and Spergen Limestones of Mississippian age; they are therefore a marine sedimentary agate. See also Shaub (1980b, p. 860-864).
2855 Upatoi Creek Agate, Georgia, for Upatoi Creek, 32o 30' 01" N and 084o 43' 39A W, Muscogee County, Georgia, Upatoi Map, USGS 7.5' x 7.5'. See also Hudson (1982, p. 158-165).
2856 Urbana Agate, Iowa, see Burry (1979, p. 1312-1324). color illustrations?
2857 Uruguay Agate, a geographic term that appears in Liesegang (1915, p. 38, 79-84, Uruguay - Achat) and is used to designate the locality from which Agate with horizontal layers (Achate mit horizontalen Lagen) are very common, Uruguay. More recent authors (e.g. Landmesser, 1984) have used the term to designate all agates that have horizontal layers regardless of source and Landmesser provided a very detailed discussion of the significance of this kind of banding as it related to the history of agate research and on the origins of agates. It is now a term of structural significance rather than source of the agate. The term is probably not meant to be used synonymously with oxyx agate which term simply implies parallel banding anyplace within the agate nodule.
2858 Uruguayan Agate, Uruguay, no description, ...agate in Government sealed drums, adv., Booth's Lapidary Supply, Rock & Gem, v. 1, no. 1, p. 28. An agate from Uruguay is pictured in the world-wide web page of the Ecole des Mines Mineral Collection Catalogue (No. 1200) that can be accessed at
2859 Uruguayan Agate, no locality, no description, adv., Le Roy Atwood, Rocks and Minerals, v. 41, no. 1, p. 100. It is unclear as to whether the reference is to locality or structure.
2860 Uruguay Sard, Uruguay, no description, adv., Ernest Meier, Lapidary Journal, v. 5, no. 5, p. 377.
2861 Uruguay Structure, a term utilized by Landmesser (1988?) to describe agate with horizontal, parallel layers, but it is probably not a synonym of onyx agate as used by Landmesser. Onyx agate may have curved bands.
2862 Usan, Scotland, for Usan House, Angusshire. Most are blue, banded agates but some white or pink are known. ...brilliant inky blue and white colors; also wax yellow---Cerachates. Centres often hollow and lined with quartz or amethyst (Heddle, 1901, p. 75, 76) would have called this area Blue Hole, which see. Agates are from lavas in the lower Old Red Sandstone of early Devonian age. The site is well described and several fine agates are illustrated by Rodgers (1975, p. 37-40, figs. 31, 32) and Macpherson (1989, p. 19, 24-27, figs. 51-55) described and illustrated materials from the collections of M. F. Heddle and R. Miln that are now in the collections of the National Museum of Scotland. Fallick and others (1985, p. 672-674) used agates from this site in oxygen isotope studies to determine temperatures under which agate formation took place.
2863 Utah Banded Agate, Utah?, no description, adv., Stardust Gem House, Lapidary Journal, v. 1, no.2, outside back cover.
2864 Utah Blue Moss Agate, Utah, no description, adv., Alpine Gems & Minerals, Lapidary Journal, v. 34, no. 1, p. 178.
2865 Utah Cycad, Utah, no description, adv., Eldon Soper, Lapidary Journal, v. 5, no. 5, p. 359.
2866 Utah Flower Agate, Utah?, no description, Utah Gems, The Mineralogist, v. 16, no. 12, p. 595.
2867 Utah Nodules, Utah?, no description, adv., V. D. Hill, The Mineralogist, v. 5, no. 11, p. 21.
2868 Utah Petrified Wood, Utah?, no description, adv., T-C Rock Shop, Sevier, Utah, 1960 Rocks and Minerals
2869 Utah Picture Jasper, Utah?, no locality, no description, adv., The Berryman Menage, The Mineralogist, v. 13, no. xx, p. yy
2870 Utah Pigeon Blood Agate, Utah?, no description, adv., Stewarts Gem Shop, Earth Science, v. 15, no. 6, p. 277.
2871 Utah Polka Dot Agate, Utah?, no description, adv., James W. Redding, The Mineralogist, v. 13, no. 2, p. 41.
2872 Utah Red Nodules, Utah, ...mottled red solids with drusy scattered pockets, adv., Beaver Canyon Campground, Lapidary Journal, v. 27, no. 1, p. 90.
2873 Utica Jewelstone of Illinois, name used by Mori (1980, p. 24-35) for cherts???????. Rockhound, v. 9, no. 3, p. xx.

About the Agate Lexicon

The Agate Lexicon and glossary of amorphous and cryptocrystalline silica gems have been designed to be used in conjunction with the Agate Bibliography, which was compiled to be used by researchers, hobbyists, historians, lapidaries and other individuals which have an interest in these stones. Numerous localities are listed here but this does not imply that the sites are available for collectors or collecting. Many of the sites are historic, depleted, are on private property or are protected by legal leases or claims and some are now on protected sites such as parks, nature preserves, or historic areas. Wherever possible, stratigraphic details are listed, but the user must always refer back to the original citations. Map information has been derived from 7.5' x 7.5' topographic maps issued by the U.S. Geological Survey (USGS) and latitude and longitude have been derived mostly from Geographic Names Information System of the USGS.

Authors should not cite the Agate Bibliography or Agate Lexicon as a source in their published or unpublished works but should cite only those publications listed therein.

Named varieties of agates, jaspers, etc., have created special problems for both scientific researchers and historians. We have recognized at least two different usages of names. Some names appear to have geologic / historic validity, as they were described along with the lithology / geography of a region. Some names were introduced simply as trade names to boost sales of gem dealers. In the former case, the name will be followed by appropriate literary citation as to who first used the name and in what context. In the latter case, an advertisement (abbreviated adv.) is the first published record or public notice. We have tried to find the earliest citation in either case and the user should keep in mind that older citations unknown to us may exist. Advertisements are not cited to generate business but to simply give a historic source; many of the firms appearing in the citations are indeed no longer in existence.

Cited materials are generally only from accessible sources such as professional journals, magazines, hobbyist journals, open file reports of government agencies, newspapers, etc. Bulletins issued by local clubs and societies are generally not cited with the exception of those special publications that were actually made for public distribution.

Wherever possible, imagery of one or more specimens of named agate varieties, structures, patterns, etc. are provided. Images have been provided by several sources and are not to be utilized in other pages without the consent of the image owner.