The temple itself was constructed of marble, and had a total of 127 columns. However, Artemis' temple was burned to the ground on July 21, 356 B.C.E. The temple was then restored, only to be destroyed again by the Goths in 262 C.E.
It often seems amazing to me that so many people know about the Parthenon and Delphi, yet few are even aware of the massive monument to Artemis built at Ephesus.
A highly recommended site regarding the temple: http://pharos.bu.edu/Egypt/Wonders/artemis.html