Sometimes called Dalmation Jasper this stone gets its name from the black spots within the matrix. Actually it is a mineral called Aplite. This is a creamy feldspar / jasper quartz material with black spotty inclusions within. Melody says these to be Tourmaline; Gienger says to be Pyroxene. I tend towards the latter, as the black spotting does not tend to have the more glassy appearance we might associate with tourmaline. Pyroxenes include Hypersthene and Diopside.
Whatever their nature, the spots provide a paradoxically grounding and uplifting effect. Interestingly this stone occurs in a few of our Ascended Master layouts, including that of Lord Lanto and Serapis Bey, wherein they act to ground Light energy into the body. Useful therefore at any energy centre, but particularly at the base or omega centres, or in the hands, to ground and balance.