The harder material between ox horn and sandalwood is ox horn. Ox horn, also known as water buffalo horn, has a hardness rating of approximately 2.5 on the Mohs scale, which is a measure of mineral hardness. In contrast, sandalwood, a type of aromatic tree, has a hardness rating of around 2 on the same scale. This indicates that ox horn is slightly harder than sandalwood. The hardness of a material is determined by its resistance to scratching, and since ox horn is rated higher on the Mohs scale, it is more resistant to scratching than sandalwood. This difference in hardness is due to the composition and structure of the materials. Ox horn is primarily composed of keratin, a protein found in hair, nails, and animal horns, which provides it with a dense and durable structure. Sandalwood, on the other hand, is composed of lignin and cellulose, which are less dense and more susceptible to scratching.