This is a vintage-style, black and white illustration of a group of rock crystals. The crystals are depicted with a high level of detail, using dense, parallel lines to create shading and texture. The crystals are primarily hexagonal in shape, with pointed tips and flat faces. They vary in size, with several large, prominent crystals dominating the composition and smaller crystals clustered around the base. The artist has used a technique of cross-hatching to create depth and dimension, making the crystals appear three-dimensional. The background is a dark, textured field, which helps to emphasize the crystals. The image is labeled 'Fig. 12. - Group of rock crystal.'