Green Agate gems are varieties of Chalcedony: a broad term given to stones made up of microcrystalline quartz Silvershake's Celtic knot jewelry in sterling silver have ancient patterns over 5000 years old Silvershake 1.12ct. Natural Emerald Green Agate 925 Sterling Silver Celtic Knot Pendant with 18 Inch Chain Necklace; is shipped to you in anti-tarnish protection inside reinforced gift boxes with satin-style pouches; guaranteed beyond competitors Silver, in its purest form, is rarer than gold, but like gold, silver is too soft. So Sterling silver is created by alloying 92.5% pure silver with 7.5% of another pure metal: usually copper Silvershake 1.12ct. Natural Emerald Green Agate 925 Sterling Silver Celtic Knot Pendant with 18 Inch Chain Necklace