dert cave ≫ rocks

Rocks & Minerals & Fossils

The purpose of this page is twofold. One, it benefits me as a "formal" catalogue of my collection. For each of my specimens I can assign them an ID and record both its general and unique traits. Two, it benefits me again as a really good excuse to prove how awesome my rocks are.

Like the gallery, specimen thumbnails have been compressed so that the page loads more quickly. As usual each specimen can be clicked on to view a larger size along with is associated information.

[Editor's Note: Photo quality heavily varies as the priority was to upload each specimen so their individual information could be recorded as this would be the most time-consuming aspect. In the future, once I sort out a proper photography setup, these lower quality images will be replaced.]

Last-Updated: 01/04/26

Count: 73

Minerals

Count: 26

Specimen Qualities

ID: #71
Species: Chalcopyrite
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Becoming a geologist has absolutely ruined any kooky rock/crystal/fossil/gem gift shop I visit.

Now I have to scrutinise every single specimen inside to figure out what is actually genuine and reasonably priced. This chalcopyrite was probably priced £3 higher than it should've been, but that was a lot fairer than the baked amethyst geodes with a price tag of £600.

The most ridiculous thing in there were these horribly preserved and prepared trilobites (a lot of remaining matrix, highly chipped specimens, etc.) priced at £8.80. For comparison, my specimen (ID #5) cost £3.

Specimen Qualities

ID: #33
Species: Tourmaline
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Tourmaline was sometimes called the "Ceylonese Magnet" due to its ability to attract and repel hot ashes due to its pyroelectric properties.

Specimen Qualities

ID: #32
Species: Smoky Quartz
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Colour is produced when radiation emitted from the surrounding rock activates colour centres around aluminium impurities within the quartz. The shaded colour allowed flat panes of smoky quartz to be used as sunglasses in 12th century China.

Specimen Qualities

ID: #31
Species: Satin Spar
Weight: Unknown
Locality: Unkown
Age: Unknown

Specimen Qualities

ID: #30
Species: Rose Quartz
Weight: Unknown
Locality: Unkown
Age: Unknown

Specimen Qualities

ID: #29
Species: Quartz
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

The second most abundant mineral in Earth's continental crust (behind feldspar)!

Specimen Qualities

ID: #28
Species: Quartz
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Quartz is the defining mineral for 7 on the Mohs scale of hardness, the qualitative scratch system for determining material hardness.

Specimen Qualities

ID: #27
Species: Pyrite
Weight: Unknown
Locality: Unkown
Age: Unknown

Specimen Qualities

ID: #26
Species: Orange Calcite
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Probably one of the more delicious looking minerals I own, on account of it looking like a huge chunk of orange.

Specimen Qualities

ID: #25
Species: Muscovite
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

This sample is shockingly reflective and required me to knock the shutter speed down to a fraction of a second for the image to not be completely overexposed, compared to around 2-3 seconds for every other specimen.

Specimen Qualities

ID: #24
Species: Labradorite
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

The specific name for the iridescence exhibited by labradorite is very appropriately called labradorescence.

Specimen Qualities

ID: #23
Species: Fluorite
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

There is something about this sample that makes it incapable to photograph well, in every setup or with any lens I have tried it has been impossible to get a sharp image of it. I can only assume it is cursed.

Specimen Qualities

ID: #22
Species: Plagioclase
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Analysis of thermal emission spectra from the surface of Mars suggests that plagioclase is the most abundant mineral in its crust.

Specimen Qualities

ID: #21
Species: Agate Slice (Dyed)
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Unsure where I acquired this considering it isn't from the "crap I bought when I was 7" collection, that features other really obviously dyed rocks.

In terms of actual agate geology, formation of the bands is poorly understood. It can't be directly observed nor have agates been successfully lab-grown.

Specimen Qualities

ID: #20
Species: Agate Slice (Dyed)
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

A specimen from the "crap I bought when I was 7" collection, with beautifully obvious dye giving it such a strong pink colouring.

Specimen Qualities

ID: #19
Species: "Citrine" (Heat-treated Amethyst)
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Likely not genuine citrine due to its rarity and instead heat-treated amethyst.

Specimen Qualities

ID: #18
Species: Calcite
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Calcite is the defining mineral for 3 on the Mohs scale of hardness, the qualitative scratch system for determining material hardness.

Specimen Qualities

ID: #17
Species: Blue Calcite
Weight: Unknown
Locality: Unkown
Age: Unknown

Specimen Qualities

ID: #16
Species: Bismuth
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Not a mineral, but considering a brick is also on this page I think it's more reasonable to include.

Specimen Qualities

ID: #15
Species: Biotite
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

If you're ever considering becoming a geology teacher within a carpeted classroom, I hope you enjoy spending half of your life picking up biotite flakes from the carpet whenever your students start peeling layers like there's no tomorrow whenever they get to handle biotite.

Specimen Qualities

ID: #14
Species: "Citrine" (Heat-treated Amethyst)
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Due to the rarity of natural citrine, most "citrine" you'll ever see for sale is actually heat-treated (baked) amethyst. You can typically tell the difference as heat-treated amethyst has a brown tint to the yellow colour or exhibits a hexagonal crystal habit (impossible for natural citrine to do).

Specimen Qualities

ID: #13
Species: Amethyst
Weight: Unknown
Locality: Unkown
Age: Unknown

Notes

Extremely weak in colour that is barely perceptible in the photo

Specimen Qualities

ID: #12
Species: Agate
Weight: Unknown
Locality: Unkown
Age: Unknown

Specimen Qualities

ID: #11
Species: Azurite
Weight: Unknown
Locality: Canary Islands
Age: Unknown

Notes

Azurite is produced by the oxidation of copper ore deposits, however because of its instability in open-air it is often pseudomorphologically replaced (crystal dimensions maintained, mineral replaced) by very green malachite.

I found, probably, the most pathetic grain of azurite on fieldwork one time, significantly smaller than a popcorn kernel.

Specimen Qualities

ID: #1
Species: Amethyst
Weight: Unknown
Locality: Unknown
Age: Unknown

Notes

Amethyst is easily one of the most well-known minerals and probably the one you're most likely to have even if you're not a rock collector.

Technically, amethyst isn't a mineral in its own right as it is actually a variety of quartz. The violet colour is the result iron impurities in the lattice. Therefore, amethyst maintains many qualities of quartz, like it's chemical resilience and hardness, that make it popular as a gemstone for jewellery.

Specimen Qualities

ID: #3
Species: Pyrite
Weight: Unknown
Locality: Unknown
Age: Unknown

Notes

"Fool's gold" is the infamous alternate name of pyrite, plaguing hopeful prospectors for centuries.

Pyrite is captivating because it's one of the few minerals that can form truly perfect cubic crystals, unfortunately my sample is much more of an anhedral mass of many crystals.

Rocks

Count: 38

Specimen Qualities

ID: #72
Species: Coal
Weight: Unknown
Locality: Wigan
Age: Carboniferous

Notes

Coal in Wigan? Inconceivable!

Specimen Qualities

ID: #70
Species:
Weight: Unknown
Locality: Unknown
Age: Unknown

Specimen Qualities

ID: #69
Species: Breccia
Weight: Unknown
Locality: Unknown
Age: Unknown

Notes

In all actuality this is probably some anthropogenic material, which would explain the hole on one side..

Specimen Qualities

ID: #68
Species: Slate
Weight: Unknown
Locality: Bethesda, Gwyned, Wales
Age: Cambrian

Notes

The property of being able to split slates into thin sheets is known as "fissility" and is why it finds common use as a roofing tile.

Specimen Qualities

ID: #67
Species: Sandstone
Weight: Unknown
Locality: Unknown
Age: Unknown

Notes

The white streaks running across the rock are most likely veins of quartz.

Specimen Qualities

ID: #66
Species: Conglomerate(?)
Weight: Unknown
Locality: Unknown
Age: Unknown

Notes

The large white crystals are quartz, seemingly forming inside a conglomerate.

Specimen Qualities

ID: #65
Species: Igneous(?)
Weight: Unknown
Locality: Unknown
Age: Unknown

Notes

The rock itself appears to be some kind of igneous rock, but the more interesting aspect is the size and amount of the quartz veins inside it.

Specimen Qualities

ID: #64
Species: Sandstone
Weight: Unknown
Locality: Unknown
Age: Unknown

Notes

The white streaks running across the rock are most likely veins of quartz.

Specimen Qualities

ID: #63
Species: Extrusive Igneous
Weight: Unknown
Locality: Nea Kameni, Greece
Age: Unknown

Specimen Qualities

ID: #62
Species: Extrusive Igneous
Weight: Unknown
Locality: Nea Kameni, Greece
Age: Unknown

Specimen Qualities

ID: #61
Species: Pumice
Weight: Unknown
Locality: Lipari Islands, Italy
Age: Recent

Notes

An excellent prank to pull on people is throwing pumice at them, scares the hell out of them until they realise how light it is. Pumice has a density lower than water. In fact, submarine or coastal volcanic eruptions have the potential to form massive floating rafts of pumice on the water.

Specimen Qualities

ID: #60
Species: Obsidian
Weight: Unknown
Locality: Anatolia, Turkey
Age: Pleistocene

Notes

Obsidian has famously had a history of use as a cutting tool. It potentially has modern potential for surgical scalpels as a much finer edge can be cut compared to contemporary materials.

Specimen Qualities

ID: #59
Species: Obsidian
Weight: Unknown
Locality: Unknown
Age: Unknown

Specimen Qualities

ID: #58
Species: Mudstone
Weight: Unknown
Locality: Yorkshire, UK
Age: Jurassic

Specimen Qualities

ID: #57
Species: Mudstone
Weight: Unknown
Locality: St David's Head, Pembrokeshire, Wales
Age: Ordovician (Arenigian)

Specimen Qualities

ID: #56
Species: Mica Schist
Weight: Unknown
Locality: Loch Clunie, Scotland
Age: Pre-Cambrian

Notes

Schists are probably the shiniest rocks you'll ever see.

Specimen Qualities

ID: #55
Species: Marble
Weight: Unknown
Locality: Isle of Skye, Scotland
Age: Tertiary

Notes

If you're taking a geology exam and you're unsure if the sample you were given is of marble or some other white rock all you have to do is use your little dilute bottle of hydrochloric acid (from the provided mineralogy kit that also includes a copper penny). Because of the calcite in marble, it will effervesce upon contact with the acid.

If it doesn't work and you're stuck on identifying the rock, simply drink the acid.

Specimen Qualities

ID: #54
Species: Igneous
Weight: Unknown
Locality: Unknown
Age: Unknown

Notes

The thick sub-parallel veins are composed of quartz.

Specimen Qualities

ID: #53
Species: Gneiss
Weight: Unknown
Locality: Evje, Norway
Age: Pre-Cambrian

Notes

The alternating dark and light coloured bands (poorly visible in this sample) is known as gneissose banding, a type of high grade metamorphic foliation.

Some of the oldest rocks in the world are gneisses, with the Acasta Gneiss of Canada being one of the oldest of the oldest.

Still not as old as your mother.

Specimen Qualities

ID: #52
Species: Gabbro
Weight: Unknown
Locality: St. David's Head, Pembrokeshre, Wales
Age: Ordovician

Specimen Qualities

ID: #51
Species: Quartz Geode (Dyed & Painted)
Weight: Unknown
Locality: Unknown
Age: Unknown

Notes

By far the funniest rock I've ever been given, so ridiculously fake and piss-yellow I can't help but adore it. I give my life to the Piss Geode. All hail.

Specimen Qualities

ID: #50
Species: Quartz Geode (Dyed)
Weight: Unknown
Locality: Unknown
Age: Unknown

Notes

My favourite from the "crap I bought when I was 7" collection, completely wrong tone to ever be passed off as amethyst and the drops of dye used on it are visible to the naked eye.

Specimen Qualities

ID: #49
Species: Crinoidal Limestone
Weight: Unknown
Locality: Derbyshire
Age: Carboniferous

Specimen Qualities

ID: #48
Species: Crinoidal Limestone
Weight: Unknown
Locality: Clitheroe
Age: Carboniferous

Notes

A nice part about this locality is that it smells rather pleasant when the pie factory nearby is active.

Specimen Qualities

ID: #47
Species: Conglomerate
Weight: Unknown
Locality: Pembrokeshire
Age: Unknown

Specimen Qualities

ID: #46
Species: Conglomerate
Weight: Unknown
Locality: Farrington, UK
Age: Cretaceous

Specimen Qualities

ID: #45
Species: Chalk
Weight: Unknown
Locality: Yorkshire, UK
Age: Cretaceous

Notes

The Cretaceous geological era actually derives its name from chalk (literally chalk-bearing) due to how common chalk beds are during that period.

Specimen Qualities

ID: #44
Species: Brick
Weight: Unknown
Locality: Rivington, UK
Age: Recent

Notes

Brick!

Specimen Qualities

ID: #43
Species: Breccia
Weight: Unknown
Locality: Ilam, Staffordshire, UK
Age: Pleistocene

Specimen Qualities

ID: #42
Species: Basalt
Weight: Unknown
Locality: Nea Kameni, Greece
Age: Unknown

Specimen Qualities

ID: #41
Species: Basalt
Weight: Unknown
Locality: Northern Ireland
Age: Tertiary

Specimen Qualities

ID: #40
Species: Basalt
Weight: Unknown
Locality: Unknown
Age: Unknown

Specimen Qualities

ID: #10
Species: Quartz Geode
Weight: Unknown
Locality: Canary Islands
Age: Unknown

Notes

Geodes form when minerals, in this case quartz, precipitate out of a solution that enters or passes through a hollow rock or cavity.

An incredibly funny specimen I was given once is another geode, but the rock was cheaply painted black and the crystals dyed a comically piss-yellow neon.

Specimen Qualities

ID: #2
Species: Quartz Monzonite
Weight: Unknown
Locality: Shap Fell, Cumbria, UK
Age: Devonian

Notes

I originally mistook this specimen for a pink granite, but the identification it came with describes it as a monzonite. It turns out it's a very similar rock in terms of formation, texture and composition that has a lower proportion of quartz. Granite has 20% quartz or more, a monzonite only has 5-20%.

Specimen Qualities

ID: #4
Species: Peridotite
Weight: Unknown
Locality: Hebei, China
Age: Unknown

Notes

The best rock.

Specimen Qualities

ID: #6
Species: Anthracite Coal
Weight: Unknown
Locality: South Wales
Age: Carboniferous

Notes

Coal is formed from low-grade metamorphism (heat and pressure acting on a rock) of organic matter, the greater the degree of metamorphism the higher the "rank" of coal. The progression goes from peat to lignite to bituminous to anthracite.

Predominantly, coal is found in Carboniferous beds which is where the name is derived from (coal-bearing).

Specimen Qualities

ID: #7
Species: Basalt
Weight: Unknown
Locality: Nea Kameni, Greece
Age: Unknown

Notes

Basalt is an extremely common volcanic rock with a low viscosity. This low visicosity allows for the formation of flood basalts which can form large igneous provinces such as the Deccan Traps of India.

I highlight this quality of basalts because the formation of LIPs is correlated with mass-extinction events throughout Earth's history. In particular I mentioned the Deccan Traps as it formed 66 million years ago, the same time as the end-Cretaceous extinction that is famous for wiping out non-avian dinosaurs. A meteorite impact (the Chixculub Impact) is popularly seen as the cause, however in reality it was likely a combination of the two.

Specimen Qualities

ID: #8
Species: Sandstone
Weight: Unknown
Locality: Penrith, Cumbria
Age: Permian

Specimen Qualities

ID: #9
Species: Ammonoid
Weight: Unknown
Circumference: 15.7cm
Locality: Unknown
Age: Unknown

Notes

I'd argue ammonoids constitute the most "iconic" marine fossils, likely owing to their spiral morphology and common nature. Although they are incredibly important palaeontologically, serving as excellent index fossils.

Other

Count: 3

Specimen Qualities

ID: #73
Name: Septarian Concretion

Specimen Qualities

ID: #35

Notes

If you ever find yourself enticed by the offer of one kilogram of biotite mica for the low low price of five Great British pounds please consider the following questions; how much biotite actually is that, what use do I have for one kilogram of biotite and where do I keep one kilogram of biotite. I considered absolutely none of these questions when making my purchase.

The mica jar is one of my most prized possessions, but this jar doesn't even contain all of it, most of it remains in the original bag.

Specimen Qualities

ID: #34

Notes

This jar contains all the smaller specimens and tumblestones from my collection. It contains gifts from an advent calendar, random fossils and stained glass.