Swans Island Indigo Based Color 70% silk/30% Seacell £5.00 This product is sold out. Contact us for availability. 0 in your basket View Basket Checkout Swan Island Indigo Basec Color. Dyed with natural indigo into a deep rich purple colours. Label does not have yardage and fibre content but I think it's pure wool, probably fingering or sports weight. Skein weighs 100g.