Good luck convincing the customers that it really is Gold Dust..
In the sun light ----that will be easy.
Crushed Iron Pyrite would look good in the sunlight too and cost a lot less and according to the Federal trade commission any product advertised or sold sold as gold must bear a quality or Karat mark specifying the content in either percentage or Karat content
It is unfair or deceptive to misrepresent the type, kind, grade, quality, quantity, metallic content, size, weight, cut, color, character, treatment, substance, durability, serviceability, origin, price, value, preparation, production, manufacture, distribution, or any other material aspect of an industry product.
(a) It is unfair or deceptive to misrepresent the presence of gold or gold alloy in an industry product, or the quantity or karat fineness of gold or gold alloy contained in the product, or the karat fineness, thickness, weight ratio, or manner of application of any gold or gold alloy plating, covering, or coating on any surface of an industry product or part thereof.
(b) The following are examples of markings or descriptions that may be misleading:2
(1) Use of the word "Gold" or any abbreviation, without qualification, to describe all or part of an industry product, which is not composed throughout of fine (24 karat) gold.
(2) Use of the word "Gold" or any abbreviation to describe all or part of an industry product composed throughout of an alloy of gold, unless a correct designation of the karat fineness of the alloy immediately precedes the word "Gold" or its abbreviation, and such fineness designation is of at least equal conspicuousness..
this is just a brief part of the rules you might want to peruse the rest, (just for your own information)
here is a link before you jump off a tall cliff.
http://www.ftc.gov/bcp/guides/jewel-gd.shtm#§ 23.1 Deception (general).
Good luck with the sales pitch