  In this paper we report a search for intermediate mass magnetic monopoles and
nuclearites using CR39 and Makrofol Nuclear Track Detectors (NTDs) of the SLIM
large area experiment, 440 m^2 exposed at the high altitude laboratory of
Chacaltaya (Bolivia) and about 100 m^2 at Koksil, Himalaya (Pakistan). We
discuss the new chemical etching and improved analysis of the SLIM CR39 sheets.
Preliminary limits are based on 316 $m^2$ of CR39 NTDs exposed for 3.9 y.
