This is Snowflake #27 in the book of 100 Snowflakes. Instructions on Page 57. Pictured on page 26 in Showcase.

“ ‘Firnspiegel’ is a term for the icy glaze that forms when snow melts and refreezes.”.

Finished diameter: 2 5/8 in. (67 mm)
Thread required: 7 yd. (6.4 m)

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