In Astrology, Mercury represents communication and logical thought, while Pluto represents transformation, intensity, and sexuality.
When your Mercury is in conjunction to your partner’s Pluto, your partner transforms your way of thinking. The Pluto person inspires the Mercury person to delve deeply into subjects. On the downside, the Pluto person may attempt to control the Mercury’s person thoughts, and may be overly forceful in imposing his views on the Mercury person. Also, Pluto may demand to know all of Mercury’s secrets, which may put Mercury on edge.
Hard aspects (square, opposition) between Mercury and Pluto in synastry share many things in common with the conjunction aspect, but are a bit trickier to handle. Pluto may demand to know all of Mercury’s secrets. Pluto’s probing could bring up Mercury’s uncomfortable secrets, leaving the Mercury person feeling “exposed.” Pluto may be too forceful in shaping and transforming the Mercury’s thoughts and ideas, which could aggravate the Mercury person.
Harmonious aspects (trine, sextile) between Mercury and Pluto in synastry indicate that the two of you will engage in deep, penetrating conversations. This exchanges will serve to stimulate your thoughts and “get to the root” of subjects and issues of interest. You find it easy to tell each other your deepest secrets.