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	 Cummingtonite Mineral Data  |  |  | 
   
| General Cummingtonite  Information  | 
|  Chemical  Formula: | [ ]Mg7Si8O22(OH)2 | 
|  Composition: | Molecular Weight = 780.82 gm | 
|  | Magnesium  21.79 %  Mg   36.13 % MgO | 
|  | Silicon    28.78 %  Si   61.56 % SiO2 | 
|  | Hydrogen    0.26 %  H     2.31 % H2O | 
|  | Oxygen     49.18 %  O | 
|  | ______        ______ | 
|  | 100.00 %      100.00 % = TOTAL OXIDE | 
|  Empirical Formula: | Mg7(Si8O22)(OH)2 | 
|  Environment: | Contact and regional metamorphic rocks. | 
|  IMA Status: | Valid Species (Pre-IMA) 1824 | 
|  Locality: | Cummington, Massachusetts, USA. Link to MinDat.org Location Data. | 
|  Name Origin: | Named after its locality. | 
|  Synonym: | ICSD 81355 | 
|  | PDF 42-545 | 
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