The Rock Library

Gneissose banding and pegmatite in an Archean granite gneiss from the Pilbara craton, Australia. These diapirs squeeze the greenstone belts.

Pyrolucite (manganese oxide) in a synsedimentary breccia formed as an Archean palaeosol on dolomite. From Pilbara, Australia.

Ripple cross lamination with hematite in the 2.5 billion year banded iron formation at Paraburdoo, Pilbara, Australia. @ImperialRSM

Conical stromatolites in the 3.43 billion year old Strelley Pool Chert in Pilbara, Australia. Old critters! @ImperialRSM

Archean jasperite at Marble Bar, Pilbara, Australia. A 3.46 billion year old chert. @ImperialRSM

Normal faults in Triassic sediments on a wavecut platform east of Watchet, Somerset. Seeing geology by drone. @ImperialRSM

@pavementgeology @ImperialRSM Hi Ruth, always retweeting when I mean to reply! This is a cool rock. Was tempted to call it a migmatite. I must come on your tour sometime.

Amphibolite with folded veins of quartz, feldspar and hornblende. St Paul's underground station, London. @ImperialRSM

Every day the Rock Library is attacked by hackers. So sorry to all the students and staff who rely on us. We are repairing malicious damage.

F2 folds with crenulation cleavage in black phyllite and metasiltstone, Falmouth, Cornwall. #fieldworkfriday for the RSM's Paul Garrard

Like a knife through butter. Cutting a slice through a basalt with a mantle xenolith - using a rock saw to make a #ThinSectionThursday

Lamproite from Oz with phlogopite phenocrysts in a groundmass with richterite and leucite. The world's deepest magma. #ThinSectionThursday

The Rock Library's Matt Genge on the rocks of Australia House in London twitter.com/rockbloke/stat…

Rock library in the field. Spindle bombs and matle xenoliths from a leucite basanite scoria cone in Sardinia @chpet @AAlechiarenza

Parallel agate-bearing vugs in a basaltic andesite sill injected into wet pyroclastics in Sardinia. @AAlechiarenza @chpet @peterophysics

Through cross beds in Triassic sandstones never fail to impress, particular in Sardinia. @AAlechiarenza @chpet @peterophysics

Metagabbro...Silurian back-arc basin magma at greenschist facies. In Sardinia...with @rockbloke @AAlechiarenza @peterophysics

Mantle xenoliths with pyroxenite veins and phlogopite megacrysts from Sardinia. Mantle fieldwork with @chpet @rockbloke @AAlechiarenza

Ignimbrite with rheomorphic flow in rotated lithic clasts. Field petrology in Sardinia with @rockbloke @chpet @AAlechiarenza @peterophysics

Nature's chocolate egg - a particulary brown agate nodule. Happy Easter from the Rock Library.