What is lost and what is kept
What goes is the weight and the depth at an edge, which on a traditional terracotta floor is half the character of the material.
What stays is the color, and the color is the point. Terracotta means baked earth, and the red is iron in the clay oxidizing in the kiln rather than a pigment applied to it. Cut the clay small and the color survives intact because it was never on the surface to begin with.
Natural, which means unglazed
Both pieces here are natural, and on a clay tile that means the fired body itself with nothing over it.
An unglazed terracotta is matte, slightly porous and warm, and it takes a patina with use rather than wearing through a coating. A glazed red tile is a different object: a hard bright glass surface over a body of any color. Terracotta tile has the material at full thickness.
Cotto is the name for what it is
The series here is Cotto, which is simply the Italian for cooked, and it is the word used across southern Europe for unglazed fired clay flooring.
Naming a product for the process rather than for a color or a place is unusual and it is accurate. There is nothing else to describe: fired clay, nothing on it, cut to a size.
Sheet sizes that are not square
The two sheets here are 12 3/8x12 3/8 and 11 1/2x14, which is the usual mosaic situation of the pattern deciding the sheet.
The coverage figure on the listing compares between them rather than the nominal dimensions, since neither lands on a clean square foot the way a plain grid would.
3/8 inch, and where it meets a terracotta floor
Both pieces are 3/8 of an inch, against the 3/4 and more that hand-made terracotta field tile runs at.
That is the figure to settle first if a mosaic band is going into a terracotta floor, which is the most obvious use for it. Half an inch of difference across a threshold is not something the joint can absorb.
The color deepens rather than wears
An unglazed clay floor changes with use, and the change goes in one direction: the surface smooths and darkens.
That happens because the color is the body rather than a layer on it, so wear removes nothing that was carrying the color. On a mosaic the effect is concentrated at the edges of the pieces, which take traffic first, and a terracotta mosaic border set into a plain floor picks up its patina faster than the field around it.
Where a terracotta mosaic goes
A border inside a larger clay floor, a backsplash, a small floor in a garden room and a panel where the color is wanted without the weight.
It is also the one way to get clay into a wet area at a small scale, since a sheet follows a curve and a fall where a thick hand-made tile cannot. Red tile and mosaic reaches the same color in other materials, and Spanish reclaimed terracotta the salvaged end of the same clay.
