مصادر الكيمياء موقع لتعليم الكيمياء بصورة مبسطة
A hard microcrystalline form of the mineral chalcedony (a variety of quartz). Typically it has greenish or brownish bands of coloration, and is used for making ornaments. Moss agate is not banded, but has moss like patterns resulting from the presence of iron and manganese oxides. Agate is used in instrument bearings because of its resistance to wear.