33. CONGLOMERATE

From the Latin word "conglomeratus" meaning "pressed together".

A clastic sedimentary rock that contains rounded or subrounded fragments (clasts) that have the size of pebbles, cobbles, or boulders (>2mm).

The rounded fragments are weathered fragments of pre-existing igneaous, metamorphic, or sedimentary rocks.

If the fragments are angular, the rock is called a breccia.

34. SANDSTONE

A clastic sedimentary rock composed of fragments that have the size of sand grains (1/16 to 2 mm). In most sandstone, the grains (clasts) are predominantly quartz and feldspar.

Other minerals such as iron-bearing minerals and micas may occur in minor amounts and may be important in determining the color of the rock.

Sandstone is used extensively as construction material.

35. LIMESTONE

The word "lim" is a Middle English word that is the same as "lime".

Lime is a white substance (calcium oxide, CaO) obtained by heating limestone.

Limestone is a sedimentary rock consisting chiefly of calcite (CaCO₃).

Limestone is the most important and widely distributed of the carbonate rocks.

It can be classified into one of three groups:

1. Organic - reef and coral limestones.
2. Chemical - deposits from sea water or fresh water.
3. Clastic - weathered fragments of organic, chemical, or other clastic limestone that have been deposited and formed into a new rock.

One of the major ingredients of cement. Also used as a building stone.

36. MUDSTONE (SHALE)

Shale is from the German word "schale" meaning " a thin layer".

Constituent grains are not detectable with the unaided eye.

A clastic sedimentary rock composed of fragments that have the size of silt or clay grains (<1/16 mm).

Mudstone is structureless (contains no thin layering) whereas shale is usually laminated, the layers being <1 cm in thickness.

Shale breaks into sheets

Smooth to very slightly gritty.