Tile is made from a range of raw materials depending on the type, but most tile falls into one of a few categories: ceramic and porcelain (made from clay, feldspar, and quartz), natural stone (cut from geological formations like marble or granite), glass, cement, or metal. The specific ingredients and how they’re processed determine everything from a tile’s hardness to where you can safely install it.
Ceramic Tile: Clay Fired at Lower Temperatures
Standard ceramic tile starts as a mixture of natural clays, water, and minerals. The clay body is shaped, dried, and then fired in a kiln at roughly 1,800°F to 2,000°F. At these temperatures the clay particles fuse together enough to form a solid tile, but the body remains somewhat porous. That’s why most ceramic wall and floor tiles get a glaze, a glassy coating applied before or between firings that seals the surface and adds color, texture, or shine.
Glazes are built around glass frits, which are crystalline minerals melted together at extremely high temperatures (around 2,600°F to 2,800°F) and then quenched in water to form a brittle, glassy material. This frit is ground into a fine powder, mixed with pigments, and applied to the tile surface before a final firing fuses it into a smooth, protective layer. The glaze is what makes a ceramic tile cleanable, stain-resistant, and available in virtually any color. Mineral pigments like iron oxide, cobalt oxide, and chromium oxide create the palette, while other compounds can produce matte, glossy, or even metallic finishes.
Porcelain Tile: Denser and Harder
Porcelain tile uses the same basic family of raw materials as ceramic, but in different proportions and fired at higher temperatures. A typical porcelain tile body is roughly 50% feldspar (a mineral that melts into glass during firing), 30% kaolin (a fine white clay), and 20% quartz. This mix, fired at temperatures above 2,200°F, produces a tile that’s far denser than standard ceramic.
The finished porcelain tile body is mostly glass. Roughly 50% to 65% of the material becomes a glassy matrix during firing, with 10% to 25% remaining as quartz particles embedded in that glass, a small amount of a crystalline mineral called mullite (under 10%), and little to no unfused feldspar. This glassy structure is what gives porcelain its low porosity, typically 3% to 7% closed pores. The result is a tile that absorbs very little water, resists staining, and holds up in freezing temperatures and high-traffic commercial spaces.
Both ceramic and porcelain tiles are rated on a durability scale from 1 to 5. Class 1 tiles are suitable only for walls or very light use, while Class 5 porcelain handles heavy commercial foot traffic. The rating reflects how well the glaze resists abrasion, which ties directly back to the composition and firing temperature of both the body and the surface coating.
Natural Stone Tile
Natural stone tiles aren’t manufactured. They’re cut from quarried rock, then shaped and finished. The composition depends entirely on geology.
- Marble is limestone that was buried deep enough to be heated and compressed until its mineral grains (calcite) recrystallized together. This makes it denser and less porous than the original limestone. The signature grey veining comes from clay layers in the original rock that got heated and swirled during the transformation.
- Granite is an igneous rock, meaning it formed from cooled magma. It’s coarse-grained and primarily made of quartz, feldspar, and mica. In the stone industry, the label “granite” is used broadly to include related rocks like gneiss and schist, which share similar mineral compositions and durability.
- Slate starts as ordinary clay-rich shale. Add heat and pressure, and those clay particles strengthen and bond into a durable, layered rock that splits naturally into flat sheets, perfect for tiles, roofing, and historically, chalkboards.
- Travertine forms from mineral-rich water, typically near hot springs. It’s made of calcite (the same mineral in marble and limestone) and has a distinctive lacy, pitted texture created by the way water flows in small rivulets away from the spring’s source. Onyx is a variation of the same stone, formed under similar conditions.
Because natural stone is porous to varying degrees, most stone tiles need to be sealed after installation to prevent staining. Marble and travertine, both calcite-based, are also vulnerable to etching from acidic liquids like lemon juice or vinegar.
Terracotta: The Oldest Tile Material
Terracotta literally means “cooked earth” in Italian, and the name is accurate. It’s made from red-burning earthenware clay, a type found almost everywhere in the world. These clays are naturally full of iron oxide, which is what produces the characteristic warm red-orange color after firing. The raw clay itself can look brown, maroon, green, or red before it goes into the kiln.
Terracotta is fired at much lower temperatures than porcelain or stoneware, with around 1,940°F considered the sweet spot. This balances strength against the stability and rich red color that lower temperatures preserve. Push the temperature much higher and terracotta starts to warp, blister, and eventually melt, because the impurities in the clay act as fluxes that lower its melting point. The trade-off is that terracotta is softer, more porous, and less durable than stoneware or porcelain. It needs sealing and isn’t ideal for areas with heavy wear or freeze-thaw cycles.
Cement Tile: No Kiln Required
Cement tiles take a completely different approach. They’re never fired. Instead, they’re made by pouring a mixture of materials into a mold and curing them under hydraulic pressure.
The decorative surface layer is a thin mixture of white Portland cement, marble dust, silica sand, calcium carbonate, and mineral pigments. Iron, cobalt, and chromium oxides provide the colors. A metal pattern, like a cookie cutter, sits inside the mold to separate different colored sections, creating the geometric and floral patterns cement tiles are known for. Beneath that pigmented layer, a thicker body of Portland cement and sand gives the tile its structural strength.
Because the color is embedded in the cement itself rather than applied as a surface glaze, cement tiles can be refinished by light sanding if they wear down over the years. They do require periodic sealing, since unglazed cement is naturally porous.
Glass Tile
Glass tiles are made from silica (the primary ingredient in all glass), often sourced partly or entirely from recycled bottles and plate glass. Post-consumer glass is collected, washed, crushed into small pieces called cullet, and then melted and reformed. Some glass tiles are made entirely from waste glass with no added resins, binders, or other additives, essentially giving discarded bottles a second life as a building material.
The glass can be formed into tiles through casting, pressing, or fusing sheets in a kiln. Color comes from mineral additives mixed in before forming, or from the original color of the recycled glass. The finished product is nonporous, stain-proof, and reflective, which is why glass tile is popular for kitchen backsplashes and shower walls. It’s not typically used on floors, since glass can be slippery and is more prone to cracking under heavy impact than ceramic or porcelain.
Metal Tile
Metal tiles are available in stainless steel, copper, brass, bronze, and aluminum. They’re not solid blocks of metal. Instead, they’re typically thin sheets of metal (16-gauge or 22-gauge stainless steel, 21-gauge copper) mounted onto a backing material like fiberboard or hardboard. Some use adhesive tape or magnetic mounting systems instead of a rigid backer.
The appeal is purely aesthetic and functional in specific settings. Stainless steel resists heat and is easy to clean, making it a common choice behind commercial stoves. Copper develops a patina over time that some homeowners find desirable. Metal tiles won’t crack like ceramic, but they can dent, scratch, and show fingerprints.
How Material Affects Where You Can Use Tile
The raw materials in a tile dictate its porosity, hardness, and resistance to moisture, which in turn determine where it belongs in your home. Porcelain’s glassy, low-porosity body makes it suitable for outdoor installations, wet areas, and commercial floors. Standard ceramic works well on walls and moderate-traffic interior floors. Terracotta and cement tiles need sealing and are best in sheltered, low-moisture areas unless properly maintained. Natural stone varies widely: granite handles kitchens and entryways with ease, while marble scratches and etches more readily and suits bathrooms and fireplace surrounds where it won’t face heavy abuse.
The water absorption rate is the simplest indicator. Porcelain absorbs less than 0.5% of its weight in water. Standard ceramic absorbs more. Natural stone, terracotta, and cement fall on a wide spectrum. If you’re choosing tile for a wet or outdoor area, the material’s composition matters more than its appearance.