Which one of the following substances is not used as a lubricant in heavy industries ?

In heavy industries, lubricants are used to reduce friction between moving parts. Sand (primarily silica) is highly abrasive and increases friction, leading to significant wear and tear; therefore, it is never used as a lubricant. In contrast, the other options are established lubricants:

• Graphene: A revolutionary solid lubricant known for its high strength and ability to significantly reduce friction and wear in mechanical systems.
• Talc: A very soft mineral (1 on the Mohs scale) with a layered structure that allows it to act as an effective dry lubricant.
• Glass: In its molten state, glass is used as a specialized lubricant in high-temperature metalworking processes, such as the hot extrusion of steel and titanium alloys, to prevent the metal from sticking to the dies.