Balangeroite

Balangeroite is classified as an inosilicate with 4-periodic single chains, Si₄O_12. It is a completely separate mineral from true asbestos. It is economically important for providing building materials, especially for thermal insulation purposes, fireproofing, etc.^[5] Recent publications by Turci^[6] have drawn some conclusions that balangeroite was not asbestos and had poor ecopersistence and biopersistence. This study also pointed out that it was the obvious chrysotile exposures there, not balangeroite, that caused the incidence of mesotheliomas.

The chemical formula for balangeroite is (Mg, Fe²⁺, Fe³⁺, Mn²⁺)₄₂Si₁₆O₅₄(OH)₄₀^[7] and it has been calculated as shown in the diagram below by Compagnoni as follows:

Table 1a. Chemical analysis of balangeroite[7]
SiO2	28.37
TiO2	0.03
Al2O3	0.27
Fe2O3	8.89
Cr2O3	0.03
FeO	16.95
MnO	3.59
MgO	31.81
CaO	0.13
H2O	9.93
Total	100.00

Wet chemical, X-ray fluorescence and electron microprobe analyses were used to deduce the composition of balangeroite.^[7] The common intergrowth with chrysotile proved to be valuable in providing better chemical resolution, as portrayed in Table 1. The results varied due to submicroscopic intergrowths or zoning. From the wet chemical analysis, there was 9.5% average weight loss after calcination at 1000 °C, due to the presence of water.^[7] This was calculated as the difference from 100% of the microprobe results, with the assumption that large quantities of material usually contain some impurities, and the possible oxidation of Fe²⁺ under heating.^[7] A ratio of Fe²⁺/Fe³⁺ = 2.12 was obtained, and on the basis of the known volume and density, the empirical formula for the unit cell was derived^[7] (Mg _25.70 Fe²⁺_7.69 Fe³⁺_3.63 Mn²⁺_1.65 Al_0.17 Ca_0.07 Cr_0.01 Ti_0.01) total = 38.93 Si_15.38O_53.66(OH)_35.92.

Balangeroite is based on an octahedral build that consists of channels that are filled by chains of silicate tetrahedra grouped in three and 4 rows running along the fiber axis.^[6] Balangeroite is isostructural to gageite.^[7]

In contrast to chrysotile, however, balangeroite has more metal ions than silicon ions and might be in some cases seen as complex iron oxide containing some type of silicate structure in its framework.^[6] The surrounding fluid takes in a large number of the cations which are octahedrally coordinated, which unlike amphiboles, may be easily removed.^[6] As a consequence, the Mg and Fe are released forcing the silicate structure to become loosely bound and therefore pass into solution.^[6] Further tests have been conducted on Balangeroite's ecopersistence and it showed fairly low eco-persistence at neutral pH.^[6] Further studies were conducted by imitating weathering in an experiment to predict if weathered fibers retain the toxic potential present in freshly extracted fibers.^[8] The tests proved that balangeroite showed the removal of Mg and Si, which shows continuous structural severance that extends far beyond the surface.^[5]

Balangeroite can develop as loose fibers or be compact when in large volumes, which can be prismatic.^[7] Antigorite flakes are included in relict prismatic balangeroite, while transmission electron microscopy observation shows that fibrous balangeroite is partially replaced by chrysotile.^[9] The fibers run for a couple of centimeters in [001].