This type of opal features dendrites, which are fern-like inclusions of iron, manganese, or other metallic oxides that create bold patterns within the gem. Typically, dendritic opals are cut into slices to best exhibit nature's artwork. As you might guess, these pieces are one-of-a-kind, as no two dendritic patterns are the same. Usually these opals are white, yellow, blue, green, or pink and show black inclusions well.