The rock , which is formed from sediments eroded off unvegetated terrestrial landscapes .
The rock , which is formed from sediments deposited in near - shore coastal environments , consists almost entirely of sand - size quartz grains held together by quartz cement .
The rock , which is formed from sediments eroded off unvegetated terrestrial landscapes and deposited in near - shore coastal environments , consists almost entirely of sand - size quartz grains held together by quartz cement .