This is one of the altars to the Four Cardinal Directions in my house.  It's archetypal symbology includes:  the pentagram (within the golden coin-like circle), which represents wealth on the material plane as found in the ancient Tarot; the diamond, as found in a standard deck of cards; the color purple, which is a sublimated or rarified Earth color; the central, womb-like geode  (which is actually translucent and can be backlit at night), representing depth, stillness, and the female principle; and standard clay bricks, which symbolize the land on which we build.  Worked into the terra cotta mortar are ashes from my deceased father, who was an excellent provider and taught me much about the physical plane. He was also a Taurus, which is an earth sign.