The Naked Scientists

The Naked Scientists Forum

Author Topic: We'd love to know how this rock formed/what it is?  (Read 3969 times)

Offline verna

  • First timers
  • *
  • Posts: 3
    • View Profile
My father-in-law found this rock between Springbok and Kenhardt in the Northern Cape in South Africa.  We'd love to know how it was formed. 


 

Offline verna

  • First timers
  • *
  • Posts: 3
    • View Profile
We'd love to know how this rock formed/what it is?
« Reply #1 on: 29/06/2010 20:56:27 »
I've got a "back" view as well
 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8126
  • Thanked: 53 times
    • View Profile
We'd love to know how this rock formed/what it is?
« Reply #2 on: 30/06/2010 01:26:22 »
snap ? ...


                                                                                                   http://en.wikipedia.org/wiki/Concretion
 

Offline Bass

  • Neilep Level Member
  • ******
  • Posts: 1340
  • Thanked: 5 times
    • View Profile
We'd love to know how this rock formed/what it is?
« Reply #3 on: 30/06/2010 02:38:19 »
Cool!  fossilized bowling balls!
Now if you could just find the pins... ???
 

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 6564
  • Thanked: 7 times
  • Moderator
    • View Profile
We'd love to know how this rock formed/what it is?
« Reply #4 on: 30/06/2010 03:38:19 »
For a mineralogist you knowledge of sedimentary rocks seems a bit limited fella - I would probably say it is a concretion.

I am too tired to type all of this myself so this is from Wikipedia

"A concretion is a volume of sedimentary rock in which a mineral cement fills the porosity (i.e. the spaces between the sediment grains). Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin con  meaning 'together' and crescere meaning 'to grow'. Concretions form within layers of sedimentary strata that have already been deposited. They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock. This concretionary cement often makes the concretion harder and more resistant to weathering than the host stratum.

"There is an important distinction to draw between concretions and nodules. Concretions are formed from mineral precipitation around some kind of nucleus while a nodule is a replacement body."

The picture below AND ITS CAPTION are from the same page - http://en.wikipedia.org/wiki/Concretion

Bowling Ball Beach



Concretions on Bowling Balls Beach (Mendocino County, California) weather out of steeply-tilted Cenozoic mudstone
 

Offline verna

  • First timers
  • *
  • Posts: 3
    • View Profile
We'd love to know how this rock formed/what it is?
« Reply #5 on: 30/06/2010 09:23:21 »
Thank you so much for your responses!  I've read your link in wikipedia and googled a little more.  I've always wondered about the formation of the rocks and mountains we see on our trips through South Africa, and I could vaguely remember bits and pieces of my school geography lessons, and I've just decided that it's time to stop wondering and start learning again!  I've just bought myself a basic geology book and I feel like a kid again :) 
 

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 6564
  • Thanked: 7 times
  • Moderator
    • View Profile
We'd love to know how this rock formed/what it is?
« Reply #6 on: 30/06/2010 17:15:20 »
Post away - we gladly answer questions - even without quoting Wikipedia when we are so rushed we can't do a proper personal answer.  Glad you have joined the group.
 

The Naked Scientists Forum

We'd love to know how this rock formed/what it is?
« Reply #6 on: 30/06/2010 17:15:20 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums