We often observe among the minerals that the most perfect specimens are found of a diminutive size; and we shall also find that the finest and purest types of the diamond occur in stones of little weight. The larger crystals, or amorphous masses, seem to be wanting in purity and brightness as compared with the lesser; and this peculiarity may be observed well marked in some of the other gems. Here, then, we may find material for the argument that the degree of brilliancy is in a measure due to the perfection of the crystallization of the stone; and, therefore, the larger and coarser the laminæ of the crystal the less will be its brightness. One thing, however, is certain; that the most brilliant gems are obtained from stones of no great weight, and which also seem, from their form, to indicate a nodular arrangement of particles in their formation; or, in other words, a certain concentric manner of crystallization. This form of deposition is not peculiar to the diamond, but is clearly shown in the sapphires, topazes, chrysoberyls, tourmalines; and the finest specimens of these gems are cut from these nodular forms. We think we are correct in stating that the greatest brilliancy and the most beautiful prismatic display may be observed in diamonds of less than ten karats in weight. In fact, the diminution of brilliancy in the gem, when above twenty karats, is easily discerned by the eye alone, as compared with the vivid and adamantine flash of a pure and perfect four or eight karat stone. The same peculiarity may be observed in the little globular masses of the chrysoberyl, which are seldom larger than a pea in size, but which, when cut, exhibit flashes of fire which are only equalled or excelled by the diamond, or the rarer zircon. We can hardly realize that the little rounded pebbles of white topaz, known as _gouttes d’eau_, “drops of water,” will yield gems of such lustre as to be often exhibited, and even sold for the diamond. Yet the larger irregular masses, or finely crystallized specimens of the same mineral, do not afford gems of unusual brilliancy. In these instances we may affirm that the form or mode of crystallization has something to do with the degree of brilliancy.