Note 29 — EXCURSION I.

The mineralogist is apt to overlook these Topazes, or to regard them as common quartz crystals, to which they bear a great resemblance, until we inspect their prisms, which will rarely be found to be six-sided; there is also another simple mark of distinction—in the quartz crystal the striated appearance on its surface is horizontal, whereas on the Topaz it is longitudinal.