R. L. Folk identifies four stages of textural maturity of sands. An immature sand consists of angular grains, poorly-sorted, with a clay matrix. Rounding of grains results in a supermature sand.
Cement consists of space-filling grains that are usually precipitated from pore water.
There is no matrix. Look closely at the quartz grains and you will see a that each contains within it the outline of a well rounded detrital grain, that has been overgrown by quartz in optical continuity, which cements the grains together and effectively fills original porosity. Note that the assignment of supermature status is based on the fact that the detrital cores of the quartz grains are very-well rounded. Much of the quartz is undulatory. As with the Lyons, rock is cemented by authigenic quartz, which overgrew well-rounded detrital grains, filling all pore space.