Which substance is an example of a mineral used in pest control?

Borax is an example of a mineral used in pest control because it is a naturally occurring mineral composed of sodium, boron, oxygen, and water. It is commonly utilized for its insecticidal properties, particularly against household pests such as ants, cockroaches, and termites. Borax disrupts the insect's digestive system when ingested, leading to dehydration and eventual death.

Other substances listed, such as pyrethrins, carbaryl, and DDT, are synthetic or naturally derived chemical insecticides but do not fall under the mineral category. Pyrethrins are derived from chrysanthemum flowers, carbaryl is a synthetic compound, and DDT (dichlorodiphenyltrichloroethane) is a synthetic pesticide that was widely used in agriculture before being banned in many places due to environmental and health concerns. Therefore, in the context of mineral-based pest control, borax is the correct and appropriate choice.