Exercise: pencil drawing of clam shell

I put this clamshell under a bright anglepoise lamp located above and slightly to the right of the shell.

I rested the shell on the spine of a book to raise it and to create some shadows.

The drawing is considerably larger than the shell itself, so the A3 sheet was quite difficult to manage. I worked initally with an HB pencil to get the general proportions and then worked it up with softer pencils, including 6B to get the darker tones.

I used a putty rubber to pick out some of the bright highlighted parts.