Stone clay is one of the newest innovations in polymer clay. These clays produce a variegated, multicolored texture, instead of the continuous tone of standard clay. You can use these clays to produce many new effects, but they require special handling for the best results.

Both Eberhard Faber (stone Fimo) and Polyform Products (Granitex) make polymer clays designed to imitate stone. Stone Fimo comes in six colors: lapis lazuli (dark blue), granite (gray), china jade (pale green), rose quartz (pink), jasper (brown), and turquoise (light blue). Granitex comes in eight colors: pink, light blue, dark blue, purple, gray, brown, orange, and green.

Granitex is softer and easier to work with than stone Fimo, which has the stiffness characteristic of Fimo. Some of the stone Fimo colors (in particular lapis lazuli and granite) are more realistic, if you are planning to use the clay by itself. All these clays come in the usual approximately-2-oz. packages; there is also a "sample pack" of Granitex containing 1 oz. of each color.

Stone clays consist of clay in a base color, plus tiny fibers in one or more contrasting colors, mixed through the clay. These fibers provide a granular appearance that (unlike marbled clay) doesn't get blended away as you work the clay.

The lapis lazuli and granite colors of stone Fimo also have metallic glitter embedded in the clay, for an even more interesting texture.

For the most part, these clays are used just like any other polymer clay. You condition, shape, and fire them the same way as regular clay.

However, because stone clay has fibers mixed with it, it needs to be handled differently when cutting. When you slice these clays with a knife (or other sharp edge, such as a cookie cutter), the fibers tend to catch on the blade and be dragged down to the bottom of the slice. This creates a dark blotch at the bottom where the fibers have clumped up. (You can try to salvage this situation by gently wiping this blotch with a piece of soft solid-colored clay; it will pick up some of the fibers.)

Because of this, you should avoid cutting stone clays with a knife if at all possible. To divide up the clay, pull off pieces with your hands, or cut it with a needle - since the needle doesn't have a sharp edge, it won't catch the fibers in the clay.

Unfortunately, the fibers make it difficult or impossible to use stone clays in canes. This is because when you slice the cane, the embedded fibers catch on the blade and drag through the clay, smearing the cane pattern. This happens regardless of how sharp your blade is; all blades seem to have this problem with the fibers.

Some of the clays are better than others at imitating stone. You can marble several colors of clay together to achieve an effect more like the irregular color patterns seen in natural stone. Try these combinations:

• gray (or granite) with blue (or lapis) and violet
• green with brown and a touch of orange
• gray with orange or pink (or rose quartz)
• translucent with one or two stone colors
• green and gray, combined with leaf green solid clay

The stone clays also take well to wet-sanding and long buffing; this creates a smooth, reflective texture like polished stone.

For a rougher, just-quarried look, roll your unfired pieces in salt, fire, then wash the salt off. The salt grains will leave tiny pits and scratches in the clay.