dert cave

Specimen Qualities

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

General Qualities

• Class: Carbonate
• Hardness: 3.504
• Habit: Varies
• Cleavage: Perfect on {011}, fair on {100}, poor on {110}
• Fracture: Conchoidal
• Colour: Deep-Blue
• Streak: Light-Bluek
• Lustre: Vitreous
• Specific Gravity: 3.78
• Other: N/A

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 dimensionss maintained, but 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, so this specimen is a marginal improvement.

Specimen Qualities

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

General Qualities

• Class: Silicate
• Hardness: 7
• Habit: Prismatic
• Cleavage: N/A
• Fracture: Conchoidal
• Colour: Violet
• Streak: White
• Lustre: Vitreous
• Specific Gravity: 2.65
• Other: Piezoelectric

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, 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

General Qualities

• Class: Sulphide
• Hardness: 6-6.5
• Habit: Cubic
• Cleavage: N/A
• Fracture: Conchoidal
• Colour: Brassy-yellow
• Streak: Greenish-black
• Lustre: Metallic
• Specific Gravity: 5
• Other: Paramagnetic

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.

Specimen Qualities

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

General Qualities

• Type: Sedimentary
• Composition: Limestone(?) infilled with Quartz
• Other: In two unequal halves

Notes

Geodes form when minerals, in this case quartz, precipitate out of a solution that enters or passes through a hollow rock or cavity. I'm not entirely certain of what the original rock in this sample is, but who cares we're here to look at it's innards.

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

General Qualities

• Type: Igneous
• Composition: Felsic
• Depth: Intrusive
• Texture: Porphyritic crystalline
• Other: N/A

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: Quartz Monzonite
• Weight: Unknown
• Locality: Hebei, China
• Age: Unknown

General Qualities

• Type: Igneous
• Composition: Ultramafic
• Depth: Mantle
• Texture: Coarse-grained
• Other: Greer

Notes

Peridotite dominates the composition of the upper regions of Earth's mantle and is thus directly inaccessible to us. So, the reason samples of it are even obtainable is because peridotite is often brought up to the surface as an inclusion in basalt lavas, as partial melting of the mantle results in a mafic magma. The black at the top of the sample (not the small crystals) is basalt.

Specimen Qualities

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

General Qualities

• Type: Sedimentary
• Composition: 86-97% Carbon
• Other: The purest form of coal and thus highest density of energy

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

General Qualities

• Type: Igneous
• Composition: Mafic
• Depth: Extrusive
• Texture: Fine-grained with vesicles
• Other: Major component of ocean crust, which is almost entirely volcanic in origin

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: Desert Sandstone
• Weight: Unknown
• Locality: Penrith, Cumbria
• Age: Permian

General Qualities

• Type: Sedimentary
• Composition: Quartz with hematite cement
• Texture: Very well sorted and rounded clasts
• Other: Horribly prone to leaving grains everywhere

Notes

Desert sandstone is the gift that keeps on giving, because if you don't secure it in some kind of container it will scatter grains of sand in every crevice nearby like there's no tomorrow.

Regardless, sandstones form from the cementation of sediments eroded out of an older parent rock, this process is the reason sands are dominated by quartz and feldspar. The composition of those two minerals make them the most resistant to weathering, while their siblings are essentially completely worn away.

Specimen Qualities

• ID: #5
• Species: Flexicalymene Trilobite
• Weight: Unknown
• Length: 6.5cm
• Width: 4.5cm
• Locality: Erfoud, Morocco
• Age: Ordovician

General Qualities

• Phylum: Arthropod
• Class: Trilobita
• Temporal Range: Mid-Ordovician - Mid-Silurian
• Other: Commonly found enrolled

Notes

Trilobites are probably my favourite animal and will be intensely familiar to anyone who's had a palaeontology lesson.

Specimen Qualities

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

General Qualities

• Phylum: Mollusca
• Class: Cephalopoda
• Temporal Range: Devonian-Cretaceous
• Other: More closely relates to squids than modern nautiloids

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 or fossils characteristic of a specific geologic period that therefore help to easily identify the age of a bed.

Later ammonoids began to exhibit "unrolled" morphologies, which resulted in some specimens living their entire life staring at their backside.