Griffin Bead Cord #12 Dark Blue is perfect for knotting pearls and beads:

This natural 100% silk cord is used for knotting Swarovski Pearls, Czech Pearls, glass beads and gemstones. Each card has an attached needle which saves you threading time. Griffin thread is very strong so doubling it is unnecessary. 

Dark Blue Griffin Bead Cord specifications:

• Product: Bead Cord
• Color: Dark Blue
• Material: Natural Silk
• Country: Germany
• Size: No.12 (0.98mm)
• Quantity: sold on cards of 2 meters 
• Other info.: Needle Enclosed