There is nothing wrong with women wearing diamond or any precious stones. Women are allowed to beautify themselves by wearing gold, silver, precious stones, etc. The only restrictions in this regard are as follows: they are not supposed to show this ornament to non-Mahram men (Mahram means the unmarriageable kin.), and they must not wear these things to show arrogance or superiority over others. The claim that wearing diamonds brings ill luck to the person has no basis in Islam.
Sheikh Muhammad Saleh Al-Munajjid, a prominent Saudi scholar, states in one of his fatwas: “Undoubtedly this is a kind of myth which has no basis in the Shari’ah. Allah, exalted be He, says concerning women: “Is then one brought up among trinkets, and unable to give a clear account in a dispute (to be associated with Allah)?” [Azl-Zukhruf 43:18]
The trinkets in which the female is brought up include gold, silver and precious stones. Allah has blessed mankind and the jinn with the things that come out of the sea and rivers such as pearls and coral. Almighty Allah says: “He has made the two seas to flow freely (so that) they meet together: Between them is a barrier which they cannot pass. Which then of the bounties of your Lord will you deny? There come forth from them pearls, both large and small.” [Ar-Rahmaan 55:19-22]
Diamonds and other kinds of precious stones are among the adornments which women are permitted to wear, but this adornment should not be shown or displayed in front of non-mahram men.
Wearing these stones is not an omen of anything, either good or bad. This is one of the false beliefs which the believer should not fall in.
However, wearing such things should not drive Muslim woman into arrogance or show-off, for this is completely rejected in Islam.”