Reflectivity of Black Particles

The Three particles below were all photographed at the same time with the same exposure and illumination. The first particle is a magnetite sphere. The second particle is a fungal spore, Nigrospora. It has a reflectivty of less than 1% in the 1.515 refractive index mounting medium that all of these particles are in. The last particle is a magnetite sphere with large crystal domains that result in more scattered light. The pattern of the ring shows regions of light and dark as a result.