Mineral:  Goethite a-Fe+3O(OH)

Sample No.: goethite.2

XRD Analysis:  Goethite and other (unidentified) contaminant.  
Sample was purified by magnetic separation.

Chemistry:  Ten microprobe analyses were homogeneous.  The 
amount of iron oxide is low for  goethite (typically 82-89%).  The 
sample probably contains elements which were not analyzed, 
accounting for the low total.  The most likely material present in a 
massive, layered sample such as this is manganite, which might well 
account for the additional overtone bands seen near 7.5 micrometers. 
However, the difference in grain shape may also produce a 
significant spectral effect in oxides.  In addition, the analysis clearly 
shows that the sample contains at least a small silicate 
contamination. Such a slightly impure composition is typical for 
goethites, so the sample was retained.

SiO2 	3.39
Al2O3	0.01
Fe2O3	75.7
MgO	0.07
CaO	0.07
K2O	0.02
TiO2	0.09
H2O	12.9
	_____
Total 	92.25
