It requires a somewhat elaborate explanation to make clear the various styles of cut without illustrations. They are usually divided into two groups, with curved, and with flat or plane surfaces. Of the first, the curved surfaces, opaque and translucent stones, such as the moonstone, cat's-eye, etc., are mostly cut _en cabochon_, that is, dome-shaped or semi-circular at the top, flat on the underside, and when the garnet is so cut it is called a carbuncle. In strongly coloured stones, while the upper surface is semi-circular like the cabochon, the under surface is more or less deeply concave, sometimes following the curve of the upper surface, the thickness of the stone being in that case almost parallel throughout. This is called the "hollow" cabochon. Other stones are cut so that the upper surface is dome-shaped like the last two, but the lower is more or less convex, though not so deep as to make the stone spherical. This is called the "double" cabochon. A further variety of cutting is known as the _goutte de suif_, or the "tallow-drop," which takes the form of a somewhat flattened or long-focus double-convex lens. The more complicated varieties of cut are those appearing in the second group, or those with plane surfaces. A very old form is the "rose" or "rosette"; in this the extreme upper centre, called the "crown," or "star," is usually composed of six triangles, the apexes of which are elevated and joined together, forming one point in the centre. From their bases descend a further series of triangles, the bases and apexes of which are formed by the bases and lower angles of the upper series. This lower belt is called the "teeth," under which the surface or base of the stone is usually flat, but sometimes partakes of a similar shape to the upper surface, though somewhat modified in form. Another variety is called the "table cut," and is used for coloured stones. It has a flat top or "table" of a square or other shape, the edges of which slope outwards and form the "bezils" or that extended portion by which the stone is held in its setting. It will thus be seen that the outside of the stone is of the same shape as that of the "table," but larger, so that from every portion of the "table" the surface extends downwards, sloping outwards to the extreme size of the stone, the underside sloping downwards and inwards to a small and flat base, the whole, in section, being not unlike the section of a "pegtop." A modification of this is known as the "step" cut, sometimes also called the "trap." Briefly, the difference between this and the last is that whereas the table has usually one bevel on the upper and lower surfaces, the trap has one or more steps in the sloping parts, hence its name.