This stitch is called Diamond Lattice. I found it in an old crochet stitch library and I am unsure of its origin. There are 4 rows to the pattern and it works up quite quickly.

You need a multiple of 10st plus 5, and then add 3 for the foundation row. I used 58ch and worked the shawl until it was 150cm or 59in long. The width was about 80cm or 30inches.