Rock Key, Selection, and Splitting

Rock Key, Selection, and Splitting

The Rock Identification- A Dichotomous Key- Interactive PDF (web version: Rock Key)

List of rock types

The rock cycle diagram

USGS Mineral Resources On-Line Spatial Data Map (select Geology/geologic map, and any other desired data– sample below)

Mineral and Rock Identification Made Easy

North East rock types/examples:


Some rocks split better than others. The quality of splitting is based on the grain or crystalline structure and cleavage planes that should be followed/mimicked when drilling- cleavages are perfect, imperfect, distinct, good, fair, and poor.  The difficulty of splitting is formally described as easy, hard, and difficult to produce. 

According to Trow and Holden’s Guide to Splitting Stone

Wedges & Shims can generally split stone up to 4-6 times the length of the wedge


1Basal or pinacoidal
3 at 90 degreesCubic
3 not @ 90 degreesRhombohedral
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