The latest discovery from the Temple Mount Sifting Project are shells from the sea-snail Murex trunculus used by Jews in Biblical times to make the blue dye Tekhelet. The dye was used to color the fringes worn on prayer shawls and 4-cornered garments, until the technique was lost.

https://templemount.wordpress.com/2017/02/02/arent-you-dying-to-know/