EARTH SCIENCE
Name: ____________
GRAPH INTERPRETATION: SANDSTONE CLASSIFICATION Period:
Date:
The graph shows a classification system for sandstones made of varying amounts of three minerals: kaolin,
feldspar, and quartz. Each corner shows a rock made up of 100% of the named mineral. The side opposite
the same corner shows rocks with 0% of that mineral but 100% of the other two minerals. Determine the
composition of a sandstone by finding the amount of each mineral in that sandstone. For example, to find
the amount of feldspar in the sandstone associated with point X, start at the “0% Feldspar” side. Count the
red lines from this side to point X. There are five lines. Each line is 10%; point X is on the 50% feldspar
line. Likewise, point X is on the 30% kaolin line, and the 20% quartz line. It also falls within the
graywacke area. Thus, point X shows a graywacke with 50% feldspar, 30% kaolin, and 20% quartz.
1. A sandstone contains 40% quartz, 30% feldspar, and 30% kaolin. What type of
sandstone is it?
2. Suppose a particular sandstone contains 95% quartz and 5% other minerals. What type
of sandstone is it?
3. What is the name and composition (list minerals & percentages) of the sandstone at point
Y?
4. What is the name and composition (list minerals & percentages) of the sandstone at point
Z?