The heart rate sensor of the Garmin Fenix 7 uses the Elevate V4 system, but the exact material composition of the sensor itself is not explicitly stated. However, it is mentioned that the sensor is located on the back of the device and is possibly made of glass, similar to other models in the series.

You will receive notifications via the smart notifications function, which is part of the smartwatch functions. This allows you to receive notifications from your smartphone [in-house data].