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Day 72 : A fine- to medium-grained quartz arenite, probably Carboniferous in age. Part of Hadrian's Wall at Chesters Fort, Chollerford, Northumberland. 

Day 71 : Sodalite, sodium aluminium silicate with chlorine. Locality unknown. Keele Collection

Day 70 : A large beryl crystal (beryllium aluminium silicate) from Miami (Mwami), Zimbabwe

Day 69 : Rhodonite, a manganese inosilicate, (Mn, Fe, Mg, Ca)SiO3, from Ekaterinburg, Urals, Russia.  Keele Cotton Collection.

Day 68 : Working from home so a boulder from the back garden collection today. It is from the Devonian of Pembrokeshire, Wales and is red siltstone with calcium carbonate nodules. I'm uncertain if the calcium carbonate is a 'primary' caliche or if they have been reworked to form a …

Day 67 : These are olivine-rich mantle xenoliths in a basalt. The sample was one of the first I collected as an A-level geology student many years ago from the Carboniferous volcanic vent at Calton Hill, near Buxton on the edge of the Peak District.  Since I collected this sample …

Day 66 : Second of Keele's open weekend specimens, this time sphalerite.

Day 65 : An open weekend at Keele so more samples from our open day displays.  This is tourmaline, probably from Cornwall.

Day 64 : Yet another common building stone, this is the Blue Yorkstone, a Carboniferous Sandstone from Yorkshire.

Day 63 : Another oolitic limestone used as a building stone.  This time it is the Monks Park Limestone, from the Monks Park Mine, Corsham, Wiltshire. It is part of the Middle Jurassic Great Oolite.