Tuff
Tuff is a type of rock that is formed from volcanic ash and other pyroclastic debris. It is a light and porous rock, often used as a building material due to its durability and insulation properties.
To be considered Tuff, the rock must contain more than 75% ash. 25-75% would be considered ‘tuffaceous’.
It can be formed by explosive volcanic eruptions or from the gradual accumulation of volcanic ash over time.
Tuff can be of interest to vulcanologists, as the layers of tuff can provide a record of volcanic activity over time.
Tuff should not be confused with tufa, a precipitated limestone.
Information about Tuff
Tuff is a rock made of volcanic ash and other small fragments ejected from volcanoes. It often looks soft, porous, and light in weight.
Textures vary from fine-grained ash that’s more uniform, to coarser varieties with pumice fragments or lithic (pre-existing rock) clasts. Colours are very variable: pale grey, whitish, yellowish, brown, sometimes even greenish, red or mixed, depending on composition and weathering.
There are also welded tuffs, where hotter ash has fused together, giving denser, harder and sometimes banded appearance.
Uses and History
Often used as a building stone in areas where it is common. It was used widely in Italy, especially by the Romans.
It is also used when crushed as an aggregate. Tuff beds are important for tephrocronology because the ash is distributed over a wide area – which makes them important for reconstructing volcanic history.
The term tuff comes from Italian tufo, used historically to refer to volcanic ash-derived rock. Societies living near volcanoes have quarried tuff for millennia for building due to its workable nature.
Many ancient cities (in Italy, for example) used tuff in walls, temples, infrastructures. Over time, extensive deposits have formed globally, from recent volcanic events to very old (even Precambrian) tuffs that have been altered.
Mineralogy
Light grey, white, yellow, brown.
Hazards and Warnings
Mineral collectors should wash their hands after handling specimens, to avoid any exposure to potential toxins.
Almost all rocks, minerals (and, frankly, almost all other substances on earth) can produce toxic dust when cutting, which can cause serious respiratory conditions including silicosis. When cutting or polishing rocks, minerals, shells, etc, all work should be done wet to minimise the dust, and a suitable respirator or extraction system should be used.
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- 凝灰岩
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- 凝灰岩
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- 응회암
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