If you feel you must include the word cosmetic, I would suggest تجميلي, but it may be an overkill.

I am pretty sure the faceplate is nothing but a piece of cheap plastic, not sapphire. It probably is greenish blue, possibly with a decorative pattern, hence "complex cosmetic."

If this is a description for a catalog of faceplates, your role maybe somewhat more complex than your usual role, extending beyond simple translation to copywriting. I would send an email to the client telling them "I feel that I need to exercise some latitude with respect to these descriptive labels for the sake of presentability to the Araic-reading customer." To exercise judicious latitude, you would need access to good pictures in full color.

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Note added at 3 hrs 23 mins (2005-05-22 04:59:07 GMT)
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ياقوت أزرق زخرفي مركب

Notice that ياقوت by itself is not a univocal term. It could mean, among other things, ruby, sapphire, or topaz.

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Note added at 22 hrs 0 min (2005-05-22 23:36:40 GMT)
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If \"complex cosmetic sapphire\" means \"the stone has a lot of different faces as in a jewel,\" I would suggest:

ياقوت أزرق زخرفي النحت
أو ياقوت أزرق زخرفي التجسـيم
أو ياقوت أزرق هندسي التجسـيم
أو ياقوت أزرق بتجسـيم هندسي