
sedimentary
Milky Quartz in Conglomerate Matrix
Silicon Dioxide (SiO2) within Clastic Sedimentary Rock
Hardness: 7 (Mohs scale), Color: White to grayish-blue quartz with reddish-brown sandy matrix, Luster: Vitreous to dull, Structure: Hexagonal crystal system (microcrystalline in this form), Cleavage: Indistinct/Conchoidal fracture
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: White to grayish-blue quartz with reddish-brown sandy matrix, Luster: Vitreous to dull, Structure: Hexagonal crystal system (microcrystalline in this form), Cleavage: Indistinct/Conchoidal fracture
Formation & geological history
Formed through the accumulation of weathered rock fragments and quartz pebbles that were cemented together by silica or iron oxide in high-energy fluvial (river) or marine environments. The quartz itself likely formed via hydrothermal veins millions of years prior to being eroded and redeposited into the sedimentary conglomerate unit.
Uses & applications
Primarily used as construction aggregate or road base material. Larger conglomerate stones are used for decorative landscaping and as historical markers in architectural foundations.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. Conglomerates like this are often referred to as 'pudding stones' when the contrast between the pebbles and the matrix is particularly sharp.
Field identification & locations
Identify in the field by looking for rounded or sub-angular pebbles embedded in a finer-grained sandy 'cement.' It will feel heavy and coarse. Commonly found in old riverbeds, glacial till, and coastal cliffs. Scratch testing the white parts with steel should leave no mark, indicating high hardness.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary