Minerals & Fossils
Minerals are naturally occurring inorganic solid materials with orderly crystal structures. Minerals are classified by their chemical composition, structure and where they fall on the Mohs hardness scale; talc being the softest and diamond the hardest. There are vast numbers and varieties of minerals, some widespread like Quartz and others not so common such as Esperite Esperite glows green under ultraviolet light somewhat like the way the fictional element Kryptonite is depicted in Superman films.
Unlike the fictional Kryptonite (said to originate from the planet Krypton) Moldavite, a green glassy material, is of extra terrestrial origin; it fell to earth as meteorites and Tektites Moldavite can only be found in Bohemia, central Europe.
Three Moldavite fragments
When I was around nine or ten years old, an aunt returning from a holiday gave me a small piece of marcisite she’d found on a Swiss mountainside; that was the start of my interest in minerals and crystals. Around the same time, my grandfather also gave me a small chunk of alabaster from the Great Pyramid in Egypt. He’d literally picked it up off the ground whilst out there during the Second World War.
I wonder about returning it to Egypt one day…
Because it lacks an orderly crystal structure the volcanic glass Obsidian (top left) is not a true mineral so it is classed a mineraloid. It was prized by primitive man for its razor sharp cutting edge. This particular example clearly shows the typical conchoidal fractures characteristic of all brittle minerals.
Top left: Obsidian ◆ Top right: Iron Pyrite
Bottom left: Iron Ore with quartz ◆ Bottom right: Iron Pyrite fossil
Iron Pyrite or Fool's Gold as it is commonly called, has a well defined crystal structure so it is classed a true mineral. This particular example displays a typical cubic crystal structure with striated sides. I have other pieces that display an octahedral crystal structure and yet more pieces with fine crystal grains; the Iron Pyrite fossil (bottom right) is a ‘replacement fossil’ where the original organic material has been replaced by fine grained Iron Pyrite.
The quartz encrusted piece of Iron Ore was collected by my brother from an iron ore mine in Western Australia in 1969.
Top left: Clear Rock Quartz ◆ Top right: Amethyst
Bottom left: Iceland Spar Calcite ◆ Bottom right: Citrine
Unlike the regular six sided crystal structure of quartz, Calcite (lower left) is a 3D rhomboid or rhombic prism. Calcite isn’t as hard as Quartz and if you hit it with a hammer it breaks into many smaller but perfectly formed 3D rhomboids.
The yellow Citrine (bottom right) rarely occurs in nature and is most likely an artificially heat treated piece of Amethyst.
It is advisable to keep all highly coloured crystals away from prolonged exposure to direct sunlight and heat sources or their bright colours will quickly fade to disappointing muted hues.
Smokey Quartz crystal ‘wand’
Like many kids, I was fascinated when I found a fossil and first heard tales of dinosaurs. I’m still enthralled by fossils and always on the lookout for new ones to add to the collection; to me a pebble beach is infinitely more interesting and rewarding than a sandy one.
Top left: a marbled scallop found at the foot of cliffs on the Greek island of Kephalonia.
Top right: a fossil sea urchin found just outside a high mountain village on Crete.
Bottom left: an unusual ammonite fragment found on my favourite beach in Dorset UK.
Bottom right: a well preserved curled Phacops or possibly Drotops Megalomanicus trilobite
It appears even the experts disagree on trilobite classifications. Last time I checked (about 14 years ago) my one looks very much like one on display at the British Natural History Museum and labelled Phacops and yet this site says: “commonly labeled (sic) as Phacops africanus, the correct scientific name is Drotops megalomanicus.” Suffice it to say, both Phacops and Drotops are members of the Superfamily Phacopoidea
I much prefer to hunt fossils in the wild (I seldom buy them) but I just couldn’t resist this fantastically well preserved trilobite I purchased from a Welsh fossil dealer; I believe it originated from North Africa.
Eye detail - hexagonal holochroal compound eyes.
Trilobites inhabited the earth throughout the Palaeozoic Era spanning 543 to 256 million years ago; a very long time before the dinosaurs became extinct 65 million years ago. These numbers are just so huge as to be almost meaningless. To try and put some perspective on it, let’s take a typical trilobite of say 400 million years as an example. Your mission (should you choose to accept) Mr Phelps is to count from 1 to 400 million at the rate of one number per second. If you did this continually for eight hours a day, five days a week, every week of the year, it would take you just over 53 years to count to 400 million!
One of my favourite finds, but perhaps not so photogenic, is this fossilised bone:
I found it many years ago amongst similarly sized pebbles on a Dorset beach near the Golden Cap which is part of the Jurassic Coast a World Heritage Site. The fossil was identified by two Lyme Regis experts as one of the front limb (flipper) bones from an Ichthyosaurus
Cut and polished petrified tree trunk cross sectional slice with Opal filled cavity (lower left)
Formed when the original organic material of the tree was replaced by minerals, this rather fine example has an opal filled cavity and the tree’s growth rings can be clearly seen.
© Tim Rainey 2006
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Last updated: 2 January 2010
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