How slate splits
Slate began as clay and mud on a sea floor, then went through enough heat and pressure to realign its minerals into parallel sheets. That alignment is called slaty cleavage, and it usually sits at an angle to the original bedding of the sediment.
A cleft slate face is therefore a plane the rock was always going to break on. A saw can cut slate flat too, and sawn slate is a different product with its own use: the color reads more evenly and the surface takes a honed or polished finish. The look most people recognize as slate comes from the split.
Gauged and ungauged
Gauging is the term to understand before ordering slate tile. Gauging grinds the back of the tile flat to a consistent thickness so the tile sets level, while the face on top keeps its cleft texture. Most of the slate at Stone Tile Depot is sold gauged.
Ungauged slate varies in thickness from piece to piece, because a natural split does not produce an even sheet. That variation has to be taken up in the setting bed as the floor is laid, which is skilled work. Gauged slate removes most of that variation from the back and leaves the textured face untouched.
Cleft, honed and polished faces
Natural cleft is the untouched split face, and a gauged tile keeps it. Honed and polished slate go a step further: the face itself has been ground, so the cleft is gone, the surface is flat and the color reads more evenly from one tile to the next. A textured 2 by 2 mosaic and a natural faced stacked mosaic in this collection sit between the two.
Polished slate is the least common of these finishes. Grinding the face to a shine deepens the color and removes the relief, so it tends to be chosen for walls, fireplace surrounds and feature panels where color matters more than texture.
Where the color comes from
Slate color is a record of the sediment it formed from. Black slate owes its color to organic carbon and graphite in the original mud. Iron oxide produces the rusts and reds of a multicolor slate, and chlorite produces the greens. California Gold, Rustic Gold, Autumn and Multi Classic belong to the multicolor group, carrying gold, rust, green and gray across a single piece.
The grading follows the color. Most of the black slates in this collection are graded low in shade variation and read fairly even across a floor, while most of the multicolor slates are graded high, so one box holds a spread of tones and the blend across a room depends on how pieces from several boxes are mixed as they go down.
Squares, planks, mosaics and pattern sets
The square is the classic slate format and it leads the collection, at 12 by 12 and 16 by 16, with 24 by 24 for a room large enough to carry it. Rectangles run 12 by 24 and 6 by 24, and Montauk Blue reaches 18 by 36, a plank long enough to change how a hallway reads.
Smaller pieces come as mosaics: 3 by 6 and 4 by 12 strips in Montauk Black, a 2 by 2 grid mounted on a 12 by 12 sheet, and a 6 by 22 stacked strip with a peel and stick back. Pattern sets in California Gold, Montauk Black and Multi Classic are sold by the set, which is how a floor of mixed squares and rectangles in one stone is usually bought.
Series names
Montauk, California Gold, Rustic Gold, Multi Classic, Autumn, Brazilian, San Rio and Premium are trade series names, not quarry designations. Montauk covers a black and a blue gray under one name, and two slates both called gold by different suppliers can come from different quarries. Matching a series and finish is the reliable way to match a stone.
Thickness from tile to tile
Slate tile in this collection runs from 0.24 inch, a thin mosaic strip, up to 0.60 inch. Gauging sets one thickness for the tiles of a given series and size, but different series are ground to different figures. The thickness is listed on each product page, which matters at a doorway where slate meets wood or carpet.
Slate and slate-look porcelain
Natural slate gives a cleft face formed by the split itself and color that runs through the body of the tile. Slate-look porcelain gives a printed face with pressed texture, an identical thickness from piece to piece and formats a quarry rarely produces. The two suit different priorities, and the slate look tile collection holds the porcelain side.
Slate for walls and small spaces
For a feature wall, slate ledger panels bond strips of split slate into units, in names that also appear on the floor tile: California Gold, Rustic Gold and Premium Black. The small formats are also grouped under slate mosaics, and the black stone on its own under black slate tiles.
