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The mineral pyrite (/ ˈ p aɪ r aɪ t / PY-ryte), [6] or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S 2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral .
The pyrite is stable until exposed to air, at which point the pyrite rapidly oxidises and produces sulfuric acid. The impacts of acid sulfate soil leachate may persist over a long time, and/or peak seasonally (after dry periods with the first rains).
[2] [7] Around the same time, the use of pyrite in construction caused similar issues for buildings in the East of Ireland. Cracking and bulging appeared in flooring concrete and other materials soon after construction. [7] [8] [3]
When grounds rich in pyrite, such as many clays or marls, are excavated for civil engineering works, the strong acidification produced by pyrite oxidation is the powerful driving force triggering TSA because it frees up and mobilizes all the ions needed to attack C-S-H and to form thaumasite (CaSiO 3 ·CaCO 3 ·CaSO 4 · 15H 2 O).
Mundic once [2] referred to pyrite, [3] but has now adopted the wider meaning of concrete deterioration caused by oxidisation of pyrites within the aggregate (usually originating from mine waste). The action of water and oxygen on pyrite forms sulphate (a salt of sulphuric acid ), thereby depleting the pyrite, causing loss of adhesion and ...
Other mechanisms have also been proposed in the literature, such as the slow and delayed release of sulfate ions by the clinker. Oxidation of iron(II) sulfides, such as pyrite (FeS 2), or pyrrhotite (Fe (1-x) S), sometimes present in construction aggregates can also represent an additional internal source of sulfate into concrete.
In this case, the pyrite has dissolved away yielding a cube shape and residual gold. This break down is the main driver of acid mine drainage. Sub-surface mining often progresses below the water table, so water must be constantly pumped out of the mine in order to prevent flooding. When a mine is abandoned, the pumping ceases, and water floods ...
The dyakis dodecahedron only exists in one crystal, pyrite. Pyrite has other forms other than the dyakis dodecahedron, including tetrahedra, octahedra, cubes and pyritohedra. Though the cube and octahedron are in the cubic crystal system, the dyakis dodecahedron and the pyritohedron are in the isometric crystal system and the tetrahedron is in ...