Fully exchanged Ag-clinoptilolite prepared at 100°C using 1 M solution of AgNO3 was studied. The initial sample (Beli Plast deposit, Bulgaria) was enriched in clinoptilolite by a sequence of treatments – crushing, sieving, sedimentation, and separation with heavy liquids to obtain a content of about 93 wt.% of clinoptilolite intergrown with opal-C. Opal-C was subsequently removed by chemical treatment. Maximum cation exchange was reached on the seventh day (4.86(4) Ag atoms per formula unit). Rietveld structural refinement was then carried out on the Ag-exchanged clinoptilolite, and three independent Ag sites were localated in the channels of the clinoptilolite structure. Seven water sites, coordinating the Ag sites, were located. Ag-clinoptilolite is, potentially, a promising low-cost antibacterial material.