Final answer:
The structural material used for Henri Labrouste's Bibliotheque Sainte-Genevieve is iron, which exemplifies the modern architecture of the era and its embrace of industrially produced materials.
Step-by-step explanation:
The structural material used for Henri Labrouste's Bibliotheque Sainte-Genevieve is iron. The library is a notable example of how modern architecture was influenced by the use of industrially produced materials, a key theme during the era following the Industrial Revolution. One of the building's most distinctive features is its iron reading room, which visually expresses the structure and provides an example of how architects of the time were exploring the potential of new materials such as iron and glass.
The use of iron in Labrouste's design was innovative for the time, and is often celebrated as an early example of the elegance and functionality iron could bring to building design. Before this period, iron was not commonly used for structural purposes in public buildings. Labrouste's work paved the way for later architectural achievements that would also use iron and steel, like Joseph Paxton's Crystal Palace, which was an early example of glass and iron construction for the Great Exhibition of 1851.