Shapes play a significant roll in stone energies. This, I myself believe, is true more so with naturally-formed stone shapes rather than artificially-shaped ones. That being said, here's some associations:
Round stones, because they are circular yet uniform, represent Magnetism and its field effect: Receptive but orderly; seemingly simple and yet intricate. This also associates the shape with reproduction for the same reasons. Rounds stones are about attraction and prosperity in all its forms.
Perfect spheres, especially those that exhibit Chatoyancy, are good from scrying (Divination).
Long, thin stones, aside from the obvious phallic association, represent Electricity and the projection of energy.
Long, round stones (often shaped like teardrops) are good for all aspects of Love because those tears can be from either Joy or Sorrow.
Egg-shaped stones not only represent fertility but also the birth of new ideas. They stimulate creativity. They can also help you discover new paths-or a way out of a blocked path or trap.
Square stones are all about solidity and stability. They keep you Grounded and, perhaps even better, they keep you Centered. Focused. They can offer great strength in times of turmoil.
Heart-shaped stones are dedicated to Love.
Triangular stones can sometimes be tricky because of their similarity to long, thin stones and Pyramid stones. They are powerful projectors and excellent for Protection.
L-shaped stones suggest a joining or juncture. It could be a crossing of paths. It could represent a radical change in path. Or it could symbolize a union such as Spiritual/Physical.
Pyramid stones, if found in Nature, are practically the ultimate in energy projection.
Diamond-shaped stones are associated with Wealth or monetary gain. This should not be confused with Prosperity as it applies to your personal, spiritual life. If you're looking for wholeness of being, happiness in heart, wisdom, etc., this is NOT the stone for it!
Other shapes generally apply to exactly what they look like. For instance, if you have a Kidney-shaped stone it would relate to the health of the Kidneys. Beyond that it can get a bit more complex and individual-oriented. The shape you see may not be one that others see in the same stone. That doesn't mean you are wrong or they are wrong. The stone simply means different things or carries different importance to each individual. For instance, I have a stone shaped like (I think) a prehistoric Giant Beaver-a creature that was native to my area eons ago.
So, not only is this an Element-induced record of past history, it also tells me something of what the stone is good for. Beavers are engineers of the highest order. They are innovative. And they work in harmony with their surroundings to the benefit of all other creatures in the area. The translation-to me-is that this is a good stone for promoting innovative ideas as they pertain to material things. If you are re-designing or attempting to improve upon something, this is a good stone to have on you. This is NOT a good stone for Revelations (coming up with something completely new) but it would be excellent for Inspirations (expanding upon a Revelation).
And so it goes. You get the idea. Hope this helped some! Blessings to you on your path of discovery!
We have seen what Power does.
We have seen what Power costs.
One is never equal to the other.