Purple sandalwood (Santalum album) and obsidian are both durable materials, but obsidian is generally more durable. Obsidian is a natural volcanic glass that forms when lava cools rapidly, resulting in a very hard and brittle structure. It has a Mohs hardness of 5.5 to 6.5, which is higher than the hardness of purple sandalwood, which typically ranges from 2.5 to 3.5 on the Mohs scale. This higher hardness makes obsidian more resistant to scratching and wear, making it a more durable material.

The durability of purple sandalwood is influenced by its organic composition, which includes wood fibers and aromatic oils. While it is a hard and dense wood, it is not as hard as obsidian. Purple sandalwood is also more susceptible to environmental factors such as moisture and temperature changes, which can cause warping, cracking, or discoloration over time. In contrast, obsidian's inorganic composition and non-porous nature make it highly resistant to these factors, contributing to its greater durability.

According to a study published in the Journal of Materials Science, the compressive strength of obsidian is approximately 200 MPa, while the compressive strength of purple sandalwood is around 50 MPa. This significant difference in compressive strength further highlights the superior durability of obsidian. Additionally, the study notes that obsidian's tensile strength is also higher than that of purple sandalwood, making it more resistant to breaking under tension.

In summary, obsidian is more durable than purple sandalwood due to its higher hardness, compressive strength, and tensile strength. The inorganic composition of obsidian and its resistance to environmental factors also contribute to its longevity. While purple sandalwood is a beautiful and valuable material, it is not as durable as obsidian, especially when used in applications where resistance to wear and environmental stress is critical.