The Islamic minaret originally evolved from a useful feature of city construction to a more revered station as the focus of the city's daily prayer. They orignally served as beacons of light (deriving from the word noor, which usually translates as light or original light) and watchtowers, while at the time 'muezzins', or criers, used the highest roof in the city for the daily call to prayer. Today a minaret is know as the slender tall tower that adorns the side of a mosque and comes from the era of the Ommayad caliphs. In this capacity, they were originally simple poles before developing into elaborate structures along with the mosques that they accompanied.
Minarets basically consist of three parts:
Base
Usually the ground underneath the towering minarets is excavated until a hard foundation is reached. Gravel and other supporting materials may be used as a foundation, and it is rare that one is built directly upon ground-level soil.
Shaft
Single minarets with in an elongated body are either conical (tapering at the top), cylindrical (a circular shaft) or polygonal (with edges as opposed to cylindrical). Stairs circle the shaft in a counter clockwise fashion, providing a necessary structural support for highly elongated shafts.
Gallery
A balcony encircles the upper section where the muezzin will give the call to prayer. It is covered by a roof-like canopy and adorned with ornamentation, such as decorative brick and tile work, cornices, arches and inscriptions. Originally plain in style, a minaret's origin in time can be determined by the level of the gallery's ostentation.
Styles and architecture can vary widely according to region and time period. Here are a few styles and the localites from which they derive:
Egypt (7th cen) / Syria (until 13th cen)Low square towers sitting at the four corners of the
mosque.
Iraq
Free-standing
conical minaret surrounded by a spiral staircase.
Egypt (15th cen)
Octagonal. Two balconies, the upper smaller than the lower, over projecting friezes of stalactite vaulting, surmounted by an elongated
finial.
Persia (17th cen)
Two pairs of slim towers flanking the mosque entrance, terminating in covered balconies and encased in blue tile.
http://www.netiran.com/Htdocs/WeeklyJournal/Art/wj01168.html
http://www.infoplease.com/ce6/world/A0833270.html