BERTL-Crystal, in Natural History, a species of what Dr Hill calls ellipomacrostyla, or imperfect crystals, is of an extremely pure, clear, and equal texture, and scarce ever subject to the slightest films or blemishes. It is ever constant to the peculiarity of its figure, which is that of a long and slender column, remarkably tapering towards the top, and very irregularly hexangular. It is of a very fine transparency, and naturally of a pale brown; and carries such evident marks of distinction from all brown crystals, that our lapidaries call it, by way of eminence, the beryl crystal, or simply the beryl.