Chalk is composed of tiny calcite (calcium carbonate) plates called coccoliths. These are sections of the intricate spherical housing secreted by a type of phytoplankton smaller than the width of a hair, known as coccolithophores.
watercolor (made with algae) on paper, 9″ x 12″
growing spiraling 
paint test strips
Artist Jennifer Parker mixes calcium carbonate with spirulina (algae) powder, gum arabic*, and water to paint botanical style paintings phytoplankton.
*Gum arabic is a natural gum that acts as a binder for paint.