Cleavages can form steps on the outside of the crystal, each parallel to the cleavage direction. How crystal habit affects luster Earthy hematite is brick red and has non-metallic luster. The crystals are so small that they are partially transparent. Light passing through the grains changes its color to red. The microscopic crystals scatter the light in all directions, giving the sample a dull appearance.
Specular hematite is gray and has metallic luster.
The crystals are large enough to be opaque. Hematite is actually a semiconductor. Here are the streak colors of five dark minerals that all appear black, dark gray, or dark brown. Notice how the streak color is more diagnostic than is the bulk mineral color. No, since the apatite dust rubs off, leaving no scratch.