Here is a list of my favorite online databases.
Mindat.org is the largest mineral database and mineralogical reference website.
WebMineral.com is a complete, up-to-date, mineral database containing 4442 mineral species descriptions and comprehensive picture library of images.
Athena is a Alphabetical list of minerals with formula and system.
Geologynet Online Geology Search Engine
www.mineralatlas.com is a database provides information about mineralogy and is dedicated to providing access to physical and chemical data, photos, electron microscopy images, images of thin sections and analytical data such as Mineral Vibrational Spectra in the near-, far- and mid- infrared regions of the spectrum, infrared emission spectra and Raman spectra of minerals.