The search of novel strains continues to be of great importance in research around the world for pharmaceutical, industrial, agricultural and biomining applications. The present study aims to investigating the microbial diversity of rock samples collected from Um Bogma formation, southwestern Sinai, Egypt which was chosen for its unique location, geological and physicochemical properties. The studied samples showed small microbial diversity and low microbial count. A total of ten isolates of actinobacteria and ten isolates of fungi were isolated and characterized phenotypically. The results indicated that all the isolated actinobacteria belong to the genus Streptomyces. They were all halotolerant with some showing antimicrobial activities when tested against Bacillus subtilis, Pseudomonas aeruginosa ATCC 9027, Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 8739, Candida albicans  and Aspergillus flavus. On the other hand, all the studied fungal isolates belong to the genus Aspergillus. They showed resistance to the antifungal nystatin when a concentration of 50 µg per ml was used. The studied locations is characterized by their harsh conditions which does not support the growth of most microorganisms which includes a temperature ranging from below 0°C at night to above 46°C throughout the day, low water content and organic matter hosting radioactive and heavy elements. Rock-dwelling microbial communities that survived such conditions open further research investigations on studying phylogenetic relationships between them as well as their possible microbial activities that can be of environmental and industrial importance.