Quartz, Amethyst, Rose quartz, malachite, jade, jasper, carnelian, Agate (particularly green ones) are all common stones that possess loving natures inherently. If you want to amplify those properties, there are several ways you can do so.
However, one of the most simple and direct is to cleanse the stone (under cold running water) and then let your energies mingle with that of the stone. Hold it in your hands. Note it's shape, color, distinguishing features, how it feels in your hand. You're learning to communicate with the stone, essentially.
Once you've reached a point where your energies and the stones are harmonious, (you may feel it grow warmer, or sense a slight tingling sensation) then tell it what you want it to do. If you want to attract loving energies, tell it to attract them. If you want to emit loving energies, do likewise. Visualization never hurts, but it's really not mandatory here.
Once you've laid your intent upon the stone, it helps to charge it.
I typically use moonlight (waxing or full)to charge energies that are passive or magnetic by nature (attracting something, drawing something toward you) and sunlight to charge stones programmed for something active or projective in nature (sending specific vibrations or qualities out into the external)
This isn't a spell per se. It's just a method of directly interacting with the energies of the stone. It resembles psychometry more than magick, but it works just as well without all the added gestures and motions.