Limestone and Clay by Lesley Glaister Secker & Warburg $170 NADIA and Simon have tried for some years to have a baby. Besides many monthly disappointments, there have been miscarriages, one of them brutally and miserably after five months. Nadia is consumed by her desire for a baby and Simon seems to be as sympathetic and compassionate a partner as a woman could wish.
Each character has a passion of a second sort, an elemental, tactile relationship with the earth. Nadia is a potter, though her depression over her inability to conceive has resulted in a ''potter's block'' that stymies her for some part of the novel.
Simon is a spelunker, a caver whose love for exploring underground Nadia opposes as too dangerous.
The novel's complication is supplied by Dan and Celia, friends of the central characters. Celia was once Simon's lover, and she is still his caving partner. Her husband Dan, previously married, has had a vasectomy. They ''hire'' Simon as a sperm donor, an occupation he agrees to in a non-clinical setting - Celia's bedroom.
She readily conceives on their first and only meeting. Some weeks later, Celia telephones Simon at home to break the good news. Simon, ever aware of Nadia's sensitivity, tells Nadia: ''It should have been yours'' without letting on that he's the father.
Celia, however, visits Nadia to confess.
The rest of the novel traces the consequences of Simon's clinical infidelity. Though Simon does not know that Nadia knows, each responds to Celia's pregnancy and Nadia's ever-darker depression with a life-threatening adventure.
