What is the chemical formula of pyrrhotite?

Pyrrhotite is an iron sulfide mineral with the formula Fe(1-x)S (x = 0 to 0.2). It is a nonstoichiometric variant of FeS, the mineral known as troilite.

What is the hardness of pyrrhotite?

Pyrrhotite (Fe1-xS, where x = 0 – 0.2) is a common sulfide mineral exhibiting a brownish-bronze color with a metallic luster. Physical properties include a hardness of 4 on the Mohs scale, a specific gravity ranging between 4.58 and 4.65 and is magnetic, but with varying intensity depending upon the iron content.

What mineral group does pyrrhotite belong to?

niccolite group
Pyrrhotite, iron sulfide mineral (Fe1–xS) in the niccolite group; in it, the ratio of iron to sulfur atoms is variable but is usually slightly less than one.

How is pyrrhotite formed?

Pyrrhotite: an Iron Sulfide Mineral Formed During Growth of Sulfate-Reducing Bacteria at a Hematite Surface.

What Colour is pyrrhotite?

1.3. Pyrrhotite (Fig. 1.11) is an unusual iron sulfide with variable iron content [Fe(1−x) S(x=0–0.2)]. The color ranges between bronze yellow and copper-red with black streak and metallic luster. The hardness varies between 3.5 and 4.5 on the Mohs scale and an average specific gravity of 4.6.

Is pyrrhotite in all concrete?

Is pyrrhotite found in every concrete foundation? No. We have tested many homes that are pyrrhotite free. The presence (or absence) of pyrrhotite depends on the rock aggregate in the concrete and where it was derived from geologically.

Is pyrrhotite a hard mineral?

At first glance, pyrrhotite can be confused with other brassy-colored sulfide minerals, but its Mohs hardness is only 3.5 to 4, and most specimens are at least slightly magnetic. No other brass-to-bronze-colored sulfides are magnetic.

Where is pyrrhotite most commonly found?

Pyrrhotite is found in basic igneous rocks, pegmatites, hydrothermal veins, and rocks associated with hydrothermal metamorphism. It is often associated with pyrite and quartz.

What is the difference between pyrrhotite and pyrite?

Pyrite is a mineral which is found in stone and produces sulfuric acid when it oxidizes upon contact with humidity and oxygen. Pyrrhotite is a mineral species composed of iron sulfide and is of a bronze yellow color, blackening when exposed to air.

How do you test for pyrrhotite in concrete?

Map cracking or spider cracking is the clearest indicator of pyrrhotite-laced concrete. In all the homes that we’ve tested and have observed map cracking, pyrrhotite has been detected. Other visual types of cracking can be ambiguous and isn’t always diagnostic without further testing.

How do I know if my foundation has pyrrhotite?

If you are looking to evaluate your own home for foundation issues, here are 5 of the most important signs of pyrrhotite issues in your foundation:

1. Exterior Grading. Always look at exterior grading and gutter systems because water can initiate problems with pyrrhotite.
2. Parge Coating.
3. Efflorescence.
4. Sandy Coloring.
5. Cracks.

Which is the correct formula for pyrrhotite minerals?

The formula of pyrrhotite minerals can also be expressed as Fe n−1 S n with n ≥ 8 to give structures from Fe 7 S 8 to Fe 11 S 12. The most iron Fe-deficient end member, Fe 7 S 8, has a monoclinic symmetry, whereas the intermediate (Fe 1−x S) and equimolar (FeS) members have hexagonal and orthorhombic structures, respectively [ 80, 81 ].

How is pyrrhotite similar to a troilite?

Pyrrhotite is similar to another iron sulfide mineral named troilite. Troilite has a chemical composition of FeS, while pyrrhotite’s chemical composition is Fe (1-x) S. Pyrrhotite is deficient in iron because some of the iron sites in its crystal lattice are vacant (empty). That is why the iron in the formula has a subscript of 1-x.

How is pyrrhotite related to other igneous rocks?

Named in 1847 by Ours-Pierre-Armand Petit-Dufrénoy from Greek πνρρός “pyrrhos”, flame-colored. Pyrrhotite is found with pentlandite in basic igneous rocks, veins, and metamorphic rocks. It is also often found with pyrite, marcasite, and magnetite. It has varying magnetic powers, depending on the number of Fe vacancies in the crystal structure.

How did pyrrhotite get its name from Greek?

Also given as Fe 1-x (x = 0 to 0.17). The various polytypes known have slightly different stoichiometries. Named in 1847 by Ours-Pierre-Armand Petit-Dufrénoy from Greek πνρρός “pyrrhos”, flame-colored.