KIRTLAND AIR FORCE BASE ALBUQUERQUE, NEW MEXICO ...

APPENDIX B
Bedding Thickness
Hardness
Fracturing
Weathering
Mineralogy (if discernible)
Other Characteristics
All classification data should be written directly on the boring log or in a field log book. The method of
deriving the classification should be described or reference to this guideline or other manuals used should
be included.
Rock Type
As described previously, there are numerous names for sedimentary rocks. In most cases a rock will be
combination of several rock types, therefore a modifier such as sandy siltstone or a silty sandstone can be
used. The modifier indicates that a significant portion of the rock type is composed of the modifier.
Other modifiers can include carbonaceous, calcareous, siliceous, etc.
Grain diameters are used for the classification of classic sedimentary rock. The following is the Udden-
Wentworth classification that will be assigned to sedimentary rocks. The individual boundaries are
slightly different than the USCS subdivision for soil classification. For field determination of grain sizes,
a scale can be used for the coarse grained rocks.
Color
Particle Name
Cobbles
Pebbles
Granules
Very Coarse Sand
Coarse Sand
Medium Sand
Fine Sand
Very Fine Sand
Silt
Clay
Grain Size Diameter
> 64 mm
4 - 64 mm
2 - 4 mm
1 - 2 mm
0.5 - 1 mm
0.25 - 0.5 mm
0.125 - 02.5 mm
0.0625 - 0.125 mm
0.0039 - 0.0625 mm
< 0.0625 mm
The color of a rock can be determined in the same manner as for soil samples. Rock core samples should
be classified while wet, when possible, and air-cored samples should be scraped clean of cuttings prior to
color classifications. Munsell Color Charts or equivalent may be used if required for the project.
Stratification
The bedding thickness designations applied to soil classification will also be used for rock classification.
Kirtland AFB
SOPs for Field Investigations B-18 April 2004