Volcanic Tuff


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Tuff, Volcanic

 

a dense volcanic rock formed by the cementation of ash, scoria, lapilli, and other éjecta from an erupting volcano. Tuffs consist of fragments of volcanic glass, pumice, and other substances; tuffs composed of whole crystals or crystal fragments are also encountered.

Tuffs are classified according to composition, nature, and fragment sizes. In terms of composition, we distinguish among rhyo-litic, dacitic, andesitic, basaltic, and other tuffs. The color of tuffs varies; Artik tuff is violet-pink, and Ani tuff is orange or yellow (both types are found in the Armenian SSR). Tuffs are formed either by direct deposition from the air during a volcanic eruption or as a result of the transport of tuffaceous material by water or wind.

Tuff is a valuable building material of excellent ornamental quality. It is used, for example, as a filler in light concrete or as a wall material. In the USSR the main tuff deposits are in Armenia. In other countries the most important deposits are near Rome and Naples in Italy and in Iceland.

V. P. PETROV

tuff, volcanic tuff

A low-density, high-porosity rock; composed of volcanic particles, ranging from ash size to small pebble size, which are compacted or cemented together; sometimes used as building stone or as a thermal insulation material.
References in periodicals archive ?
breakage, volcanic tuff and quartz sand are the effective components for the production of composite gypsum binders.
Volcanic tuffs have three different groups as follows: Gulludag Tuff, Melendiz Tuff and Alacasar Tuff.
Typically the windows are only one to five hectares in area and are completely encompassed by volcanic tuff.
thick dipping at a 25 to 35 degree angle in an altered silicified volcanic tuff.
Prospect is hosted in altered felsic and mafic volcanic tuffs.
Unlike the Fish Lake Valley prospect it is a more traditional bulk mining target which covers an area of clay altered Caetano, and Fish Creek formation Tertiary volcanic tuffs.
The samples had a total weight of 2400 kg and consisted of volcanic tuffs.
Exposed sediments in the new fossiliferous area are mostly silty sand and silty clay horizons interbedded with a number of volcanic tuffs and basaltic flows suitable for dating.
The Veta Minitas area is underlain by felsic volcanic tuffs, breccias and intrusive rocks with minor andesite flows; the same package of rocks hosting the Carmen deposit.
Adjacent to the north of an ultramafic volcanic contact are a suite of dominantly felsic to intermediate volcanic tuffs which host a main gold zone within 20 m of the contact and above the main zone, one sometimes two subsidiary zones.
The area is underlain by felsic volcanic tuffs and flows similar to those underlying Carmen, although the Veta Minitas area is much less affected by faulting than Carmen.
PilaGold discovered gold mineralization in stockworks and disseminations hosted by quartz-sericite-pyrite altered volcanic tuffs and intrusive dykes.