We use cookies to show content based on your preferences. If you continue to browse you accept their use and installation. More information. >

FMF - Friends of Minerals Forum, discussion and message board
The place to share your mineralogical experiences

FMF English Forum is moderated by John S. White and Peter Megaw
 

Spanish message board






Newest topics and users posts
20 Aug-14:32:05 Re: posters (Raystraw)
20 Aug-12:26:51 Re: collection of firmo espinar (Firmo Espinar)
20 Aug-12:16:31 Re: posters (Tobi)
20 Aug-11:57:17 Re: east coast mineral and fossil show 2019 (Tony L. Potucek)
20 Aug-11:45:36 Re: need help to confirm the composition of some specimens (Dany Mabillard)
20 Aug-10:40:00 Re: east coast mineral and fossil show 2019 (John S. White)
20 Aug-09:52:58 Re: posters (Raystraw)
20 Aug-09:27:14 Re: east coast mineral and fossil show 2019 (Bob Harman)
20 Aug-07:12:21 Re: posters (Tobi)
20 Aug-06:53:45 Posters (Raystraw)
20 Aug-05:58:11 Re: east coast mineral and fossil show 2019 (Vic Rzonca)
20 Aug-05:42:53 Re: east coast mineral and fossil show 2019 (John S. White)
20 Aug-02:42:58 Re: need help to confirm the composition of some specimens (Tobi)
20 Aug-02:33:19 Re: east coast mineral and fossil show 2019 (Tobi)
19 Aug-14:01:15 Re: east coast mineral and fossil show 2019 (Vic Rzonca)
19 Aug-02:10:14 Re: what have i found? (Steveb)
18 Aug-18:58:52 Re: what have i found? (Navieko)
18 Aug-14:48:40 Re: what have i found? (Steveb)
18 Aug-12:46:16 Re: collection of tobi (Tobi)
18 Aug-10:53:55 Re: what have i found? (Vic Rzonca)
18 Aug-10:04:44 Re: collection of michael shaw (Michael Shaw)
18 Aug-09:54:36 Re: collection of tobi (Michael Shaw)
18 Aug-08:51:18 Re: collection of tobi (Dany Mabillard)
18 Aug-08:34:25 Re: collection of tobi (Tobi)
18 Aug-07:22:41 Re: what have i found? (Navieko)

For lists of newest topics and postings click here


RSS RSS

View unanswered posts

Why and how to register

Index Index
 FAQFAQ RegisterRegister  Log inLog in
 {Forgotten your password?}Forgotten your password?  

Like
57549


The time now is Aug 20, 2019 15:44

Search for a textSearch for a text   

A general guide for using the Forum with some rules and tips
Does anyone know what the proper name for "Jack Rock" is?
  
  Index -> FOR BEGINNERS: What is it? Where is it from?
Like


View previous topic :: View next topic  
Author Message

GenericSchlub




Joined: 11 Aug 2019
Posts: 1
Location: Kentucky

View user's profile

Send private message

PostPosted: Aug 11, 2019 14:31    Post subject: Does anyone know what the proper name for "Jack Rock" is?  

For starters, I apologize for not being an expert in minerals or geology. I came here to ask questions of the experts, however. From the time I was a baby until even now as an adult, everyone I have known has referred to a specific type of rock as "Jack Rock." It's orangeish, highly dense, disproportionately heavy when compared to it's size, and hard enough to chew off the sides and blades of a plow, bush-hog, or tiller when hit.

It's definitely not sedimentary and it's not flint; and I have sometimes noticed crystals inside of broken chunks. In my entire life, I have only found two or three "Jack Rocks" with crystals inside of them, though. Attached is a photo of one that I dug out of my field earlier today. I live in the southern half of the Appalachian mountains, if that helps to identify it.

If anyone can identify it, can you please tell me the following:

What's it actually called?

Why is it so darn heavy?

Why is it strong enough to break a solid steel plow when hit?



100_3506.JPG
 Description:
Appalachian Mountains, Kentucky
Around 15-20cm Diameter
"Jack Rocks" can range from smooth pebbles in rivers to almost as large as a large dog. The biggest I have seen personally was around the size of a commercial coffeemaker.
 Viewed:  332 Time(s)

100_3506.JPG


Back to top
Reply to topic Reply with quote
Like
   

John Betts




Joined: 07 Jun 2012
Posts: 146
Location: New York City

View user's profile

Send private message

PostPosted: Aug 11, 2019 18:45    Post subject: Re: Does anyone know what the proper name for "Jack Rock" is?  

I suggest contacting the nearest college/university with a geology department, or the state geological survey. Also try searching Google for "Mineral Club Directory" to find the local mineral club, they will help you.
_________________
John Betts
Back to top
Reply to topic Reply with quote
Like
   

Kevin Conroy




Joined: 03 Dec 2018
Posts: 50
Location: Saint Louis, Missouri

View user's profile

Send private message

PostPosted: Aug 11, 2019 18:55    Post subject: Re: Does anyone know what the proper name for "Jack Rock" is?  

The Following is from "COAL RESERVES OF EASTERN KENTUCKY" by J. W. HUDDLE, E. J. LYONS, H. L. SMITH, and J. C. FERM. (GEOLOGICAL SURVEY BULLETIN 1120):

The Sandstone Parting coal bed has been mined extensively in the
Log Mountain area of the Middlesboro subdistrict, especially along
Bennett and Stony Forks, Clear Creek, and Little Clear Creek, in
the Fonde quadrangle. It is about 200 to 250 feet below the Poplar
Lick bed and about 250 feet above the Mingo coal (fig. 11). The
sandstone parting, for which this bed is named, ranges from a fraction
of an inch to 3 inches in thickness and varies in position from the
top to the bottom of tte coal bed. It is pyritic, dark in color, and
tends to adhere to the coal so that some coal is lost in cleaning. This
parting and also the coal bed are known locally as the "Jack Rock."


If this is what you have, it appears to be a dense sandstone that contains pyrite, which would make it heavy for its size.

However, everything that I've written above could be REALLY wrong. If you could provide a close-up of the stone, especially if you happen to have a piece with the crystals in it, that would be very hepful.
Back to top
Reply to topic Reply with quote
Like
   

Dale Hallmark




Joined: 16 Jun 2014
Posts: 188
Location: Texas Panhandle


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Aug 12, 2019 13:05    Post subject: Re: Does anyone know what the proper name for "Jack Rock" is?  

A picture where the rock isn't whited out by sunlight might help. Kinda reminds me of a sicilicified dolostone.

Dale
Back to top
Reply to topic Reply with quote
Like
   

Bob Harman




Joined: 06 Nov 2015
Posts: 571
Location: Indiana


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Aug 12, 2019 15:33    Post subject: Re: Does anyone know what the proper name for "Jack Rock" is?  

Notice the rock's oval to rounded shape. The rock's identity might depend upon exactly where in Kentucky it was found. If found in the Central part of the state, South of Louisville down toward Lake Cumberland and on South to the Tennessee border, it just might be a geode with some remaining attached limestone matrix. If found in the eastern part of the state, South and East of Covington and Lexington it would not be a geode as none are found there.

I suggest cracking it open with a sledge hammer. If quartz with a central cavity, it might have druzy crystals (as originally noted by the poster). Then you will have it's identity. BOB
Back to top
Reply to topic Reply with quote
Like
   
Display posts from previous:   
   Index -> FOR BEGINNERS: What is it? Where is it from?   All times are GMT - 5 Hours
Page 1 of 1
    

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


All pictures, text, design © Forum FMF 2006-2019


Powered by FMF