I've looked in lots of books on hardscaping and I quite often see projects where 2 different materials meet. It's quite common. You may want to go to the library or a bookstore and look at hardscaping books for ideas. They all do the transitions a bit differently. What I like is when the materials come together cleanly, and then use plants to soften the transition. If you have an arbor or pergola at the juncture, grow big vines on it. If not, is there room for some small soft shrubs, one on each side to act as a "gate"? If you do this, be sure to allow for adequate growth of the shrub, and don't make the opening feel narrow. If not room for shrubs, use soft sprawly perennials near the edges to join the areas together. (lavender, coreopsis moonbeam, catmint, daylilies, etc.)

Have fun!

Thank you for that suggestion. There is room at the transition point, which is about 6' wide, for vines or "gate" plants. Your suggestion to look at books is good, and I have been doing that. I've seen different materials used together, but haven't been able to figure out why I like it in some applications, but not in others. Wanting to be successful in my own garden, I turned here for advice. Thanks!