Praise be to Allaah.
The scholars have based the conditions of the hijaab (covering) which Muslim women must wear in front of non-mahram men on the evidence in the Qur’aan and Sunnah. So long as a woman adheres to these conditions, she may wear whatever she likes in public places and elsewhere, and her hijaab will be considered Islamic. These conditions may be summarized as follows:
The hijaab must cover her entire body
It should be thick enough to conceal what is underneath it
It should be loose-fitting, not tight
It should not be so attractive as to call men’s attention to it
It should not be perfumed
It should not be a dress of fame and vanity (i.e., it should be extravagant or excessively opulent)
It should not resemble the dress of men
It should not resemble the dress of kaafir women
It should not be adorned with any crosses or pictures of animate beings
Further discussion of each of the above points will appear soon, in sha Allaah.