Tomahawk crystal shape

Crystalline Habit. a-Lactose hydrate crystals are observed in a wide variety of shapes, depending on conditions of crystallization. The principal factor governing the crystalline habit of lactose is the precipitation pressure, the ratio of actual concentration to solubility (Herrington 1934A). When the pressure is high and crystallization is forced rapidly, only prisms form. As precipitation pressure lessens, the dominant crystal form changes to diamond-shape plates, then to pyramids and tomahawks, and finally, in slow crystallization, to the fully developed crystal. These types of crystals are illustrated in Figure 6.2. 

Figure 6.2. The crystalline habit of lactose a-hydrate. (A) Prism, formed when velocity of growth is very high. (B) Prism, formed more slowly than prism A. (C) Diamond-shaped plates transition between prism and pyramid. (D) Pyramids resulting from an increase in the thickness of the diamond. (E) Tomahawk, a tall pyramid with bevel faces at the base. (F) Tomahawk, showing another face which sometimes appears. (G) The form most commonly decribed as fully developed. (H) A crystal having 13 faces. The face shown in F is not present. (I) A profile view of H with the tomahawk blade sharpened. (From van Krevald and Michaels 1965. Reprinted with permission of the Journal of Dairy Science 48(3), 259-265.)...

The crystals of a-hydrate lactose usually occur in a prism or tomahawk shape. The latter is the basic shape and all other shapes are derived from it by different relative growth rates of the various faces. The shape of an a-hydrate lactose crystal is shown in Figure 4-17. The crystal has been character-... 

---