Washington County, New York
Sand grains made of quartz and a larger, multicolored quartzite pebble
were rounded by abrasion in moving water, perhaps on an ancient beach.
Later, they were cemented by dolomite to form sandstone. Look for the
concentric shapes in the dolomite crystals. These are growth zones,
formed as the crystals grew to fill the spaces between the sand grains.
The rhombic pattern is typical of dolomite. The quartzite is an earlier
generation of sandstone that was metamorphosed, deformed, eroded, and
recycled as a grain in this younger rock.
Crossed polarizers with gypsum plate