How do we cement sediments together? What kind of material cements sediments together to form rocks?
Lithification is the term used to describe any process that turns sediments into sedimentary rock. This can be accomplished through some combination of compaction and cementation. Compaction is the packing together of grains, reducing the pore space between them, and can be caused by burial beneath more sediment. Cementation is when naturally formed cement is precipitated around the sediment, holding the grains together in a consolidated form. This can occur from groundwater moving through the sediments and leaving elements behind in the sediment as it flows. Some sedimentary rocks can also form by mineral crystallization. This is when elements of the grains and cement react to form new minerals that grow in an interlocking arrangement and hold sediment grains together. ======================== I hope this is helpful.
Portland cement, which is kilned lime with other chemicals added, is commonly used to make concrete, or to cement sediments together. Nature forms rocks from sedimentary material under high pressure and heat. Pressure without heat compresses sediment in a purely mechanical process, until grains interlock forming a soft stone like sandstone. With pressure and heat, a metamorphosis occurs with chemical reactions of the sediments and formation of crystals to combine the sediments into a hard rock.
Most often the process of cementing sediments together (in nature) is done by groundwater transporting minerals to the pore spaces between the sediment grains. The minerals crystallize out of the water to form a cement that holds the grains together to produce a sedimentary rock. As to the type of materials that can act as a cement, the list would be very long as almost any mineral can fill in the pore spaces to act as a cement. But, there are a few that are very common, calcite and quartz. Other cements that I have personally seen also include gypsum, itacolumite, chrysocolla, copper, gold, silver, halite and even ice.
