Pebbles are made up of a variety of minerals, which are the building blocks of rocks. The specific composition of a pebble depends on the type of rock it came from, but some common minerals found in pebbles include:

* Quartz: A hard, glassy mineral that is often found in light-colored pebbles.

* Feldspar: Another hard mineral that can be white, pink, or gray.

* Mica: A mineral that has a shiny, flaky texture.

* Calcite: A soft mineral that can be white, gray, or brown.

* Hornblende: A dark, green mineral that is often found in igneous rocks.

* Pyroxene: Another dark mineral that is often found in igneous rocks.

In addition to minerals, pebbles can also contain other elements like iron, magnesium, aluminum, and potassium. The specific elements present will depend on the geological history of the pebble.

Here are some examples of common types of pebbles and their typical composition:

* Granite pebbles: Quartz, feldspar, mica

* Basalt pebbles: Pyroxene, hornblende, plagioclase feldspar

* Limestone pebbles: Calcite

* Sandstone pebbles: Quartz, feldspar, mica, cemented together with silica or calcite

* Shale pebbles: Clay minerals, quartz, feldspar

It's important to note that this is just a general overview, and there are many other minerals and elements that can be found in pebbles. The best way to determine the exact composition of a pebble is to have it analyzed by a geologist.