A control mechanism comprises a housing defining an interior and an exterior, an aperture formed in the housing and extending from the interior to the exterior thereof, an actuator on the interior of the housing, proximate the control aperture, and a control member positionable within the aperture to operate the actuator. The control member comprises a first surface exposed to the exterior of the housing, a second surface proximate the actuator within the housing, and a body portion extending therebetween, the body portion being formed of a substantially single crystal aluminum oxide material. A bias member is configured to bias the body portion of the control member toward an inner surface of the housing, such that the control member is retained within the aperture in operation of the actuator.