When white is right (GC-12)
The world abounds with color, but sometimes only white is the right color.
Manufactured products that require white filler of pigment materials
include paints, rubber, plastics, cosmetics, pharmaceutical products,
paper coatings, and a host of other important everyday items. Indiana
contains many limestones with the proper chemistry for use as filler. Some
appear white, but many shades of white occur. Testing at the Indiana
Geological Survey determines if these limestones are white enough.
Geologists describe rock colors in the field by using a color chart. The
chart is based on hue, value, and saturation. More refined measurements
are made in the laboratory by a photometer or a reflectance meter. Simple
calculations with these measurements allow precise determination of
Our Hoosier State Beneath Us: