Those of you who haven't actually handled projectile points before, the biggest surprise might be how tiny they are. (We call them lithics or projectile points rather than arrowheads because not all were used for arrows.) The scale bar in the picture is 2 cm; the largest point shown here is less than an inch-and-a-half long. The second surprise is the craftsmanship that went into them. Last summer I tried my hand at flaking obsidian. It isn't hard, but I need to gain control, precision, and an ability to read the stone before I'll make a recognizable arrowhead, much less beauties like these. The edges of these points are made up of literally dozens of separate flakes, many of which are only clearly visible under magnification.
You will notice the completely different pen-and-ink technique on FF# 168: It is drawn with a pattern of dots, not lines, because it is made from a grainy, sedimentary stone. The other two are made from cryptocrystalline silicate (the most-recognized kind of CCS is agate), which breaks like glass, giving the sharply-defined flake scars and reflective surface that is best shown through the linear, hatching technique.
These drawings do not look like photographs; they purposely ignore the coloring pattern of the stone and emphasize the flaking pattern, showing details which would never show up under any one set of lighting conditions.
My guides for lithic illustration are The Student's Guide to Archaeological Illustrating by Brian Dillon, to which I refer all the time, and Lithic Illustration by Lucille Addington, which I have checked out via interlibrary loan, but cannot yet afford!
(Many thanks to the Kalispel Tribe and Dr. John Dorwin for permission to reproduce my drawings here!)