We are so conditioned to associate the heart shape with the word love that it is a popular practice to use a heart in the place of love on bumper stickers and tee shirts.
There is a plant from ancient Greek times named Silphium that has a seed that looks like our modern day heart symbol. Silphium is kind of like an enormous fennel that grew along the coast of Egypt, which is across the Mediterranean Sea opposite of Greece. It was a popular healing herb, spice and even a form of birth control. Greek and Roman writers and poets wrote about it. It became so popular that by 100 AD, it was utilized to the point of extinction.
Although natural state crystals seem best for healing plants and animals, there are several manmade shapes that muscle-test very strongly for healing and balance for people, specifically sphere, pyramids, and heart shaped stones. Some of the best of the heart shaped stones or heart shaped gemstones are the puffy hearts. In addition to the heart shape of the three dimensional puffy heart, there are shapes of heart stones that are flat or asymmetrical.