Can a geologist help?

[mr dazzler]

I am certain my neighbur's think I'm nuts, every so often I swoop down to pick up a piece of gravel off the drive, not just any stone mind, but the ones that have perfect little holes through them. I have maybe 20 of them looped onto a bit of string (yeah sad isnt it I should get out more ), but new ones come up every so often. Is there anyone as knows exactly how you get these real hard stones with round small holes in them, especially how do the holes come out so uniformly round? Its a mystery to me. I dont think neolithic men drilled them, there must be a geologic explanation I am sure
Any ideas? Cheers Jonathan

 

[EdS]

the pixies do it while you are asleep.

Ed (BSc Earth Sciences) S

 

[perpetualelevator]

Tiny sand worms imported from Arrakis to start a Spice industry here on Earth. Start stockpiling your water.

How small are the holes? Sometimes water can erode holes through flat stones, but the smallest I've seen I could probably put my thumb in. It happens when water flowing over the stone catches on an imperfection and creates a little eddy, then as sediment gets picked up, it swirls around in the eddy, eventually eroding a round hole through the rock. They also come is large sizes, as I've sat inside one with three other guys.

 

[mr dazzler]

The stones are very hard only 20 mm or so gravel, the holes are 2-3 mm diameter and generally perfectly round. I'll post a picture to confound the pixies and fairy's
I saw some of those pot hole sort several times in the river tees on the sandstone layers in the waterfall's, some were 10-12 inch deep like little cauldron's

 

[Doc]

Possibly crinoid fossils, also known as St Cuthbert's beads?

http://www.nhm.ac.uk/nature-online/earth/fossils/fossil-folklore/fossil_types/crinoids02.htm

Post a pic if you can.

 

[sam_acw]

They are made my magic and are therefore lucky. I have believed this for many years and have found that I am luckier with a magic stone with a hole in it in my pocket than I would be without

 

[mr dazzler]

Heres a few close up pics, the stones are about 15-25 mm across

 

[Shewie]

A couple of suggestions Jonathan


1. They could be formed by gas escaping when they were created in lava form.

2. Or they were created by sea creatures which bury themselves into soft rock on the sea bed.


Rich

 

[Robby]

My guess would be inclusions (little bits of) softer material eroded out faster than the surrounding Matrix(main stuff that's left of the stone). This could be done as a resuslt of volcanic or depositional formation.

OOOrrrrrrr the faireies could have done it. The Orcadians call them "peedie stanes" and they're seen as good luck charms.

 

[stevesteve]

Hi Dazzler,

I used to collect these when I was little as I wondered if they were magical. These look like flints, the most common constituant of gravels that you can buy in the UK (as opposed to broken/crushed stone such as crushed granite etc).

The cause of voids in flints? Quite often these mark the moulds of fossil sponges. Sponges being silicate seem to have been a common focus for the deposition of flint in chalk. Sometimes you can find completely hollow flints which contain a 'chalk flour' including microscopic silica sponge spicules.

When I was an undergrad, one of my lecturers showed a slide of a chalk section which had been annotated with a marker pen to indicate various features... including one band of flints that some joker had labelled as 'dinosaur farts'!

Either way they are millions of years old... and still magical.

Cheers,

Steve

 

[mr dazzler]

Thanks for the replies lads
What amazes me is that if they have been made into gravel from smashed up bits of bigger rock's, why the holes stayed in tact (if they were made first?), you would of expected the stones to brake where there was holes wouldnt they of been weak points in the rock mass?
Interesting phenomenan though all the same. I remember my grandfather used to find these long bullet shaped fossil/stones he said they were remain's of octopus creatures or some thing like that

 

[stevesteve]

Ah, those are belemnites. The modern cuttlefish is a squid-like critter with the cuttlefish 'bone' in the middle of it's body. The extinct belemnite animal was similar. An elongate body much like a squid with the bullet-shaped hard parts in its centre which found today as fossils.

The flints formed in a variety of sizes, the silica crystalising out of water trapped within the forming chalk. Apart from a little wear and tear from being rolled around as river/beach gravel they may have been that size for ever. Of course some flints grew very big there are some ploughed out of the fields around me that are a foot across... and I've still never tried to make fire from flint despite it being on my doorstep. A resulution for the new year!