Diatoms are single-celled alga which have a cell wall of silica. Many kinds are planktonic, and extensive fossil deposits have been found. When we were in the Garden this week, at the home gardening center, I noticed that many of the plants had been dusted with a fine white powder. I asked a gardener if it was an insecticide? In a sense is was and it wasn’t. It was diatomaceous earth.

Composed from the bones of millions of microscopic diatoms that over the millennia had built up into a sedimentary layer, diatomaceous earth is sold as a natural alternative to chemical insecticide. Its sharp silica bones act as an irritant to insects, getting into their exoskeleton’s joints and tearing them up. It is less dangerous to humans than conventional insecticides, but care in its handling must still be taken. It is much safer to the environment than most insecticides.

In the play that we saw this week, Mlima’s Tale, the actor portraying the elephant Mlima, first smears his torso and face with white powder, evoking the ritual body painting of African tribes. This powder has a way of transferring itself, as an emblem of complicity, as each player playing a link in the chain that is the illegal ivory trade, is marked with a white powdered handprint on their bodies. In this instance the white powder was likely talc, but I wonder if the choice of its white color was supposed to be evocative of powdered ivory. Powder created when the ivory tusks are carved into objects d’art, their final form.