How to draw pearls and coral

How to draw 3D jewelrly, pearls and coral, with mixed media on gray paper. 3D drawing of a ring by Marcello Barenghi http://www.marcellobarenghi.com
Final picture: http://www.marcellobarenghi.com/2013/05/drawing-rose-ring.html
Music: "trance-candy" Royalty-free music from Free Stock Music http://freestockmusic.com
Used tools:
pasteboard (vegetal paper - light gray) 35x25 cm 1,5 mm, typically used for frames, cartonnage and binding),
9B, 7B and B pencils (Caran d'Ache grafwood),
paper stomp,
Ecoline
colored pencils (Caran d'Ache Supracolor Soft Artis),
fibre tip pens (Staedtler Noris Club 320 Double Ended Fibre Tip Pens),
markers (Tria Letraset),
pens (Pitt artist pen Faber-Castell and Stabilo Felt Tip)
black and white acrylic (Decoart and Pebeo)
white gel pen (Pentel Hybrid Gel Grip k118-LW)
brush Lefranc & Bourgeois 2 INT 1 polyamide effilé-tapered polyamid
Time taken: 4 hours and 5 minutes