Conglomerate is a coarse-grained sedimentary rock. It is a mixture of pebbles of many different sizes and sand all cemented together, mostly made up of quartz pebbles and quartz sand grains.
How was it formed?
On beaches, river banks and lake shores, sand and pebbles are deposited. They are usually rounded because they have been water-washed. Over time they become buried and compacted by the weight of sediments above them and are cemented together by chemicals dissolved in the water percolating through them.