Celtic Triquetra Knot Protection Amulet Black Agate Heart Pendant Necklace Best Amulets Collection. Celtic Triquetra Knot Protection Amulet Black Agate Heart NecklaceCeltic Triquetra Knot Protection Amulet Black Agate Heart Pendant Necklace Pendant Size: 45mm (about 2 inches) Comes in Black Agate Gemstone and Stainless Steel Celtic Charm Comes with Adjustable Necklace, Shortest: 17 inches, Longest: 24 inches Comes with Branded Packaging