Pegmatite rhymes with:
hematite, apatite, appetite, biotite, hematite, magnetite, airtight, apartheid, apatite, appetite, biotite, hematite, loctite, magnetite, sticktight, tripartite, watertight
Pegmatite sounds like:
pageant, pagnotta, passante, passionate, peasant, pequignot, pheasant, piacente, picante, pigment, pigmied, pignato, piquant, pizzimenti, poignant, poisoned, poissant, poussaint, poussant, pusant