Breccia

is a term most often used for clastic sedimentary rocks that are composed of large angular fragments (over two millimeters in diameter). The spaces between the large angular fragments can be filled with a matrix of smaller particles or a mineral cement that binds the rock together.

Stream

Conglomerate

is a clastic sedimentary rock that contains large (greater than two millimeters in diameter) rounded clasts. The space between the clasts is generally filled with smaller particles and/or a chemical cement that binds the rock together.

Stream

Arkose 

is a detrital sedimentary rock, specifically a type of sandstone containing at least 25% feldspar. Arkosic sand is sand that is similarly rich in feldspar, and thus the potential precursor of arkose. Quartz is commonly the dominant mineral component, and some mica is often present.

Stream

Wacke ("wacky")

is a name for a poorly sorted sandstone, a mixture of grains of sand, silt and clay size. Graywacke is a specific type of wacke. (more below)

Wacke contains quartz, like other sandstones, but it also has more delicate minerals and small fragments of rock (lithics). Its grains are not well rounded

Deep Marine

Shale

is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable.

Deep Marine

Chalk

is a soft, white, porous sedimentary carbonate rock, a form of limestone composed of the mineral calcite.

Marine

 Micrite

= lime mud; CaCO₃, the mineral calcite. Micrite is the equivalent of clay (rock = shale) in clastics.

This specimen could have come from a tidal lake, or a subtidal lagoon, or some similar environment.

Marine Reef

Oolitic Limestone:

A limestone composed mainly of calcium carbonate "oolites", small spheres formed by the concentric precipitation of calcium carbonate on a sand grain or shell fragment.

Deep Marine

Mermaid Scales

Travertine

is a form of limestone deposited by mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and even rusty varieties.

Cave or Marine.

Calcarenite

is a type of limestone that is composed predominantly, more than 50 percent, of detrital (transported) sand-size (0.0625 to 2 mm in diameter), carbonate grains. The grains consist of sand-size grains of either corals, shells, ooids, intraclasts, pellets, fragments of older limestones and dolomites, other carbonate grains, or some combination of these

Marine

Coquina

("co-KEEN-a") is a limestone composed chiefly of shell fragments

Sea shells stuck together and used for roads in Jamaica.

Shallow Marine, Reef

Rock Salt

Evaporative Environment

Rock Gypsum

is a sedimentary rock, typically found in thick beds or layers.  It forms in lagoons where ocean waters high in calcium and sulfate content can slowly evaporate and be regularly replenished with new sources of water.

Evaporative Envirnoment

Chert

is a microcrystalline or cryptocrystalline sedimentary rock material composed of silicon dioxide (SiO2). It occurs as nodules, concretionary masses and as layered deposits. Chert breaks with a conchoidal fracture, often producing very sharp edges.

Deep Marine