Thinking of how Mercury (the chemical element) isn't soluble in water and how Mercury (the planet) is fallen in Pisces, a water sign.... also thinking of how as an element it's not a good conductor of heat and astrologically it's in detriment in Sagittarius, a fire sign

Also thinking of how it rules Virgo and Gemini, signs concerned with the processing and quantifying of information, and how as an element its most popular and common usage is to measure quantities of temperature and pressure (specifically air, *cough* airy Gemini *cough*)

Also thinking of how it forms and is found in the Earth's crust, in rocks... and how the planet rules and is exalted in Virgo, an earth sign