Quartz is a mineral compound known chemically as silicon dioxide (SiO2). It is one of the most abundant minerals found on Earth, often forming large, distinct crystals. Pure quartz, in its natural state, is virtually non-porous and does not absorb water. This inherent water resistance is a direct result of its stable chemical composition and rigid internal arrangement.
The Molecular Structure of Quartz
The inherent water resistance of quartz stems from its crystalline structure. Quartz is built from a three-dimensional network of silicon-oxygen tetrahedra, where a central silicon atom is bonded to four oxygen atoms. This structure is extremely dense and tightly packed. Strong covalent bonds link the silicon and oxygen atoms in a continuous, interlocking pattern. This structural arrangement eliminates open spaces or microscopic channels within the mineral’s interior. Consequently, water molecules cannot penetrate the crystal lattice to be absorbed internally.
Natural Quartz vs. Engineered Quartz Surfaces
The term “quartz” is often used to describe both the pure mineral and engineered surfaces, which leads to confusion about water absorption. Natural quartz, the mineral, is pure silicon dioxide and is inherently non-porous. Natural quartzite, a metamorphic rock composed mostly of quartz, can exhibit varying levels of porosity and sometimes requires sealing.
Engineered quartz, commonly used for countertops, is a composite material made primarily of natural quartz. It consists of 85% to 97% crushed quartz aggregate mixed with polymer resins, pigments, and other materials. The resin, typically 3% to 15%, acts as a binding agent that fills minute gaps between the crushed particles. This manufacturing process creates an extremely dense, homogeneous, and non-porous slab highly resistant to water absorption.
Porosity and Practical Water Resistance
Porosity refers to the percentage of open space within a material, which directly affects its ability to absorb liquid. Because of the resin binder, engineered quartz surfaces have very low porosity, with measured water absorption rates as low as 0.02% by weight. This non-porous quality makes engineered quartz highly effective at resisting stains. Liquids like coffee, oil, or wine cannot seep into the material’s surface to cause discoloration. For this reason, high-quality engineered quartz does not require any topical sealing. This is a contrast to many natural stone countertops, such as granite or marble, which are naturally porous and rely on periodic sealing.