Brucite
- ️Thu Sep 10 2009
| Brucite | |
|---|---|
 |
|
| General | |
| Category | Mineral |
| Chemical formula | Mg(OH)2 |
| Strunz classification | 04.FE.05 |
| Identification | |
| Color |
white, pale green, blue, gray; honey-yellow to brownish red |
| Crystal habit | platy or foliated masses and rosettes - fibrous to massive |
| Crystal system | Trigonal (Hexagonal Scalenohedral) |
| Cleavage | perfect 0001 |
| Fracture | irregular |
| Tenacity | sectile |
| Mohs scale hardness | 2.5 to 3 |
| Luster | vitreous to pearly |
| Streak | white |
| Diaphaneity | transparent |
| Specific gravity | 2.39 to 2.40 |
| Optical properties | Uniaxial (+) |
| Refractive index | nω = 1.560 nε = 1.580 |
| Birefringence | 0.020 max. |
| Other characteristics | Pyroelectric |
Brucite is the mineral form of magnesium hydroxide, with the chemical formula Mg(OH)2. It is a common alteration product of periclase in marble; a low-temperature hydrothermal vein mineral in metamorphosed limestones and chlorite schists; and formed during serpentinization of dunites. Brucite is often found in association with serpentine, calcite, aragonite, dolomite, magnesite, hydromagnesite, artinite, talc, and chrysotile. Notable locations include Wood's Chrome Mine, Cedar Hill Quarry, Lancaster County, Pennsylvania.
Contents
Discovery
Nemalite
Brucite was first described in 1824 and named for the discoverer, American mineralogist, Archibald Bruce (1777–1818). A fibrous variety of Brucite is called Nemalite. It occurs in fibers or laths, usually elongated along [1010], but sometimes [1120] crystalline directions.
Industrial applications
Brucite is used as a flame retardant and also constitutes a significant source of magnesium for industry.
Magnesian attack of cement and concrete
When cement or concrete are exposed to non negligible concentration of Mg2+, e.g. when these materials are left in prolonged contact with sea water or brines, Mg(OH)2 precipitates under the high pH conditions prevailing in the cement porewater. The neoformation of brucite, an expansive material, induces mechanical stress in the hardened cement paste and is responsible for the formation of cracks and fissures in concrete.
The use of dolomite as aggregate in concrete can also cause the magnesian attack and should be avoided.
See also
- List of minerals
- List of minerals named after people
- Cement
- Concrete
- Portlandite, Ca(OH)2
References
- Lee, Hyomin; Robert D. Cody, Anita M. Cody, Paul G. Spry (2000). "Effects of various deicing chemicals on pavement concrete deterioration". Mid-Continent Transportation Symposium 2000 Proceedings. http://google.com/search?q=cache:ALh-pHYB_L0J:eco-solutions.net/Effects_of_Various_Deicing_Chemicals.pdf+concrete+brucite+magnesium&cd=6&hl=en&ct=clnk. Retrieved 2009-09-10.
- Lee, Hyomin; Robert D. Cody, Anita M. Cody, Paul G. Spry (2002). "Observations on brucite formation and the role of brucite in Iowa highway concrete deterioration". Environmental and Engineering Geoscience 8 (2): 137–145. doi:10.2113/gseegeosci.8.2.137. http://eeg.geoscienceworld.org/cgi/content/abstract/8/2/137. Retrieved 2009-09-10.
- Wies aw, W; Kurdowski (2004-09). "The protective layer and decalcification of C-S-H in the mechanism of chloride corrosion of cement paste". Cement and Concrete Research 34 (9): 1555–1559. doi:10.1016/j.cemconres.2004.03.023.
- Biricik, Hasan; Fevziye Aköz, Fikret Türker, Ilhan Berktay (2000). "Resistance to magnesium sulfate and sodium sulfate attack of mortars containing wheat straw ash". Cement and Concrete Research 30 (8): 1189–1197. doi:10.1016/S0008-8846(00)00314-8.