Saturday was an Urban Sketchers day, so I headed down to the NHM to my beloved mineral room to squint at the fabulous specimens in their glass cases. For my next three gem cards, I want to do opals, tourmalines and beryls, and I fancied including some crystals and a massive. This sort of drawing is pretty intense, partly because these objects were rather small, and because crystal growth is relatively new to me. As usual, angles and proportion are very important, and to get an accurate representation, one must pay attention to them. Click on any of them to get the full picture.