The use of natural and artificial cementitious and pozzolanic materials is gaining importance and become an essential component in today's cement-based materials. Supplementary cementitious materials are recognized to provide an added value to concrete/mortar both for mechanical and durability performances as well as to their sustainability with reduced environmental impacts of the construction industry. Developing locally produced natural pozzolans is vital in the efforts towards enhancing the construction industry's sustainability. Locally extracted raw soil from Nizwa city (NZS) in Oman was ground, calcined, characterized, and used at 10%, 25%, 35%, and 50% as partial replacement of ordinary Portland cement (OPC) in mortar mix. The blend mortar was assessed with regard to compressive strength and durability properties. The obtained results indicate a slight reduction in the flow of the blended mixes. An insignificant effect of the NZS replacement on the hardened mortar's density was observed while slightly reduced strength at 1-day and 28-day for some replacement levels. Meanwhile, around a 1% reduction in the porosity and absorption. Blended cement mortar with NZS demonstrated adequate resistance to sulphuric acid and (sulphate + chloride) exposure with lower weight and strength losses compared to the control mortar.