Glass is as strong as aluminium when used as a beam in either a vertical or horizontal situation. A glass beam is constructed from layers of toughened glass laminated together. The number of layers and thickness of the glass will be dependent on the span needed.
For stability it is necessary for either end of the beam to be secured and this is most usually done with a stainless steel shoe, into which the beam is structurally bonded. However they can also be bolted to a plate if preferred. This is purely an aesthetic decision which should be made with consideration to the finishes.
If both the vertical and horizontal span needs support then a glass "hockey stick" is used, where a mortise and tendon joint is created by staggering the layers of glass. This hockey stick of glass is stabilised by virtue of the silicone bond to the glass it supports.