The principle outcrop of serpentinite in Anglesey is near Rhoscolyn, from where I collected this specimen. The main component of the serpentinite is serpentine, which is serpentin-ized gabbro. It is a brecciated rock with inclusions of calcite. When handled it has a very "soapy" feel.
This specimen of bastite serpentine is from Kynance cove in Cornwall. Serpentinite is a coarse grained rock composed of one or more of the serpentine minerals. Heat and pressure was applied to peridotite as it moved upwards from the moho, the resulting metamorphic process creating serpentinite. The primary serpentine mineral at Kynance cove is bastite sepentine, the other being tremolite.
This concretion was collected a few days ago, August 2021. The location is a quarry at Bwlch-y-Sarnau in Powys. The detail in this cone in cone variety of concretion is outstanding, with high detail in the cross section, and very pronounced cone tops. It appears to be a broken section of a much larger rock. The detail is so clear that the specimen could be a helpful aid in understanding the formation and growth of concretions. This specimen is now in the possession of Tim Holt Wilson.
Schist is a medium grade crystalline metamorphic rock. It's metamorphism from mudstone, shale, or sometimes igneous rock, is the result of higher pressure and temperature, than that needed to form slate. The crystals are larger than those of slates, and are visible to the unaided eye. Several minerals can determine the type of schist, i.e. garnet schist, talc schist, graphite schist, chlorite schist, but the most common type of schist is mica schist. Mica schist contains quartz with biotite mica or muscovite mica as the dominant minerals. This specimen from Ontario in Canada displays the silvery appearance that is attributed to muscovite mica.
Augen gneiss is a medium to coarse grained metamorphic rock composed of mainly quartz and feldspar with smaller amounts of mica. The especially large megaclasts of feldspar are called "augens" which is German for eyes. Gneiss is formed by high temperature and high pressure action on formations of igneous or sedimentary rocks. This specimen was collected from Easter Ross in the Scottish highlands.