Conglomerates contain at least 30% of rounded to subangular clasts larger than 2 mm (0.079 in) in diameter, e.g., granules, pebbles, cobbles, and boulders.
However, conglomerates are rarely composed entirely of gravel-size clasts.
Typically, the space between the gravel-size clasts is filled by a mixture composed of varying amounts of silt, sand, and clay, known as matrix.
If the individual gravel clasts in a conglomerate are separated from each other by an abundance of matrix such that they are not in contact with each other and float within the matrix, it is called a paraconglomerate.
Paraconglomerates are also often unstratified and can contain more matrix than gravel clasts.
If the gravel clasts of a conglomerate are in contact with each other, it is called an orthoconglomerate.
Unlike paraconglomerates, orthoconglomerates are typically cross-bedded and often well-cemented and lithified by either calcite, hematite, quartz, or clay.

The differences between paraconglomerates and orthoconglomerates reflect differences in how they are deposited.
Paraconglomerates are commonly either glacial tills or debris flow deposits.
Orthoconglomerates are typically associated with aqueous currents.
Conglomerates contain at least 30% of rounded to subangular clasts larger than 2 mm (0.079 in) in diameter, e.g., granules, pebbles, cobbles, and boulders. However, conglomerates are rarely composed entirely of gravel-size clasts. Typically, the space between the gravel-size clasts is filled by a mixture composed of varying amounts of silt, sand, and clay, known as matrix. If the individual gravel clasts in a conglomerate are separated from each other by an abundance of matrix such that they are not in contact with each other and float within the matrix, it is called a paraconglomerate. Paraconglomerates are also often unstratified and can contain more matrix than gravel clasts. If the gravel clasts of a conglomerate are in contact with each other, it is called an orthoconglomerate. Unlike paraconglomerates, orthoconglomerates are typically cross-bedded and often well-cemented and lithified by either calcite, hematite, quartz, or clay.
The differences between paraconglomerates and orthoconglomerates reflect differences in how they are deposited. Paraconglomerates are commonly either glacial tills or debris flow deposits. Orthoconglomerates are typically associated with aqueous currents.
Conglomerate (geology)