Walking along the beach in Nantucket, one can hardly avoid treading on a carpet of exquistely colored scallop shells. Creamy whites, burnt oranges, gun metal and pearly grays, milky yellows, stark whites, variegated stripes.

The classic shape of the scallop shell lends itself beautifully to applique. You could do a bedspread with all the shadings and variations of the shells, each in fine cotton fabrics, strewn onto sand-colored linen. But he sure to keep the spontaneity of the design by "scattering" your shells realistically - some overlapping in clusters, and some off to themselves.

American Indian craftsmen have inset turquoise and black, semiprecious stones into scallop shells to turn them into dramatic pieces of jewelry, you can do the same in fine needlepoint, delineating the pattern by alternating your bands of "color" in turquoise, black and white. Then cut it out, line it and pad it slightly to make an unusual piece of fabric jewelry.

Borrowing from the Indians still further, you could work in real metal threads to make a shell pendant. Instead of metal, use silver gilt or Lurex threads (a synthetic available in notions departments), couching them down row by row on fine linen to make a regal shell pendant.

To get the design just right, use a real scallop shell as a model. You could use graph paper, but the easiest is to use soft tissue paper and do a "rubbing." Move the pencil back and forth over the paper and the shell, and the shell's "spines" will appear on the paper.

Now, to transfer the shell shape onto fine linen, just slide carbon paper face down between the tissue paper (on top) and the cloth (underneath) and outline neatly and clearly. If your paper design is not clear enough, accentuate it with a sharp-pointed permanent felt tip pen once you're done.

Next, you'll "pad" the shell for a three-dimensional effect, with felt that you stitch down in each spine, in graduated sizes, until the third of fourth piece exactly fits the spine. (If you've decided to couch with gold threads, use yellow felt, if you're using silver threads, use gray felt.)

Now you're ready to "couch" - which means laying down the metal threads and holdings them in place with silk or cotton threads in matching color. Take two strands of the silver or gold Lurex or Japanese silver gilt thread and one thread of DMC cotton in a fine needle (No. 8 or No. 10 crewel).

Thread the needle and pull the cotton once or twice through a cake of beeswax to strengthen it. Then couch back and forth across the shell, turning around at the edge and coming back over the padded surface in the other direction.

When you're finished, cut the linen away, turn the raw edges in and hem a silk lining, leaving two openings at the top to thread a silky cord through, so that you can hang the pendant around your neck.