The jagged Hajar Mountains, which form a backbone down the east of the country and into Oman, are composed of ophiolite rocks that rose from the ocean bed under the influence of volcanic eruptions in the former Sea of Tethys.
The beaches of this prehistoric sea were pushed into folds, a phenomenon that is easily visible in many places. These limestones mountains contain marine fossils, like corals and sea urchins.
The Hajar and Musandam mountains abound with many types of rock, both loose (and collectible) and embedded as strata in other rocks. Seams of marble, mica or quartz can easily be seen on vertical rock faces. Quartz is a mineral defined by its chemical composition and crystal structure.