Benny and Alice are describing the property of hardness, which is often used to identify specific mineral families.
<u>Explanation:</u>
The properties like streak, cleavage, luster, specific gravity, crystal habit, fracture, and color that of minerals do not make specific families of minerals based on that particular property.
On the other hand, the hardness of the minerals is used to identify them with their families depending on how hard the mineral is.
The metallic minerals are usually harder than rocky minerals.
