This crystal is commonly referred to as a U-drop prism, and it is most commonly associated with Library Lamps of the Victorian kerosene era
This particular lamp crystal is clear and has a body length of 3" (not including the top bead), but is available in smaller and longer lengths, and several different colors
The U-drop prism is comparatively inexpensive and very versatile in application
They may be used on hanging fixtures, sconces, table lamps, and even some candle sticks