If your soil is 'black', which would indicate to me that it is high in
organic material and 'loamy', then I don't see how it could have a lot of
clay as well.

You cant really tell anything about the chemical properties of soil by
examining the physical properties. The color dosent matter, yet customers are
always asking for "that black dirt". The assumption that if something is dark
in color, then it must be good soil, is wrong. For the original poster, keep
adding compost and stay away from sand and gypsum, which cost alot and dont
really help.

Toad