This is Snowflake #12 in the book of 100 Snowflakes. Instructions are on Page 49. It is pictured on Page 22 in Showcase.

“Frazil is a type of flowing ice that forms in turbulent water.”

Finished diameter: 2-1/2 in. (64 mm)
Thread required: 4 yd (3.7 m)

All pattern samples in this book are made with size 10 thread and a size 5 (1.9 mm) crochet hook.