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
21 Aug-00:27:05 Re: "deep sea manganese nodule".... (Mathias)
21 Aug-00:21:28 Re: ferberite, pyrite, siderite, and..... ? (Mathias)
20 Aug-15:02:19 Re: franjungle collection (Franjungle)
20 Aug-04:40:01 Re: micro photos of inclusions in quartz (Zbhjzm)
20 Aug-04:17:26 Re: crystal cavity + green vein poss. Chlorite? (Kara)
20 Aug-03:22:15 Re: ferberite, pyrite, siderite, and..... ? (Jorge Santos Garcia)
20 Aug-03:18:56 Re: collection of heimo hellwig (Heimo Hellwig)
20 Aug-03:06:27 Re: crystal cavity + green vein poss. Chlorite? (Peter Lemkin)
19 Aug-23:04:59 Re: question about fluorite on quartz (Robert Seitz)
19 Aug-20:11:06 Re: ferberite, pyrite, siderite, and..... ? (Justin Hickok)
19 Aug-17:07:41 Re: collection of heimo hellwig (Franjungle)
19 Aug-16:31:42 Re: question about fluorite on quartz (Protium)
19 Aug-16:11:36 Re: collection of fiebre verde - coscuez (#708) (Fiebre Verde)
19 Aug-14:07:39 Re: crystal cavity + green vein poss. Chlorite? (Kara)
19 Aug-13:27:25 Re: crystal cavity + green vein poss. Chlorite? (Peter Megaw)
19 Aug-13:03:34 Re: crystal cavity + green vein poss. Chlorite? (Peter Lemkin)
19 Aug-12:45:44 Re: question about fluorite on quartz (Peter Megaw)
19 Aug-09:49:30 Re: question about fluorite on quartz (Protium)
19 Aug-09:35:37 Re: question about fluorite on quartz (Peter Megaw)
19 Aug-08:54:35 Re: question about fluorite on quartz (Protium)
19 Aug-08:48:14 Re: crystal cavity + green vein poss. Chlorite? (Peter Megaw)
19 Aug-08:37:38 Re: mineral id help. (Matt_zukowski)
19 Aug-08:34:17 Re: ferberite, pyrite, siderite, and..... ? (Mathias)
19 Aug-08:29:08 Crystal cavity + green vein poss. Chlorite? (Kara)
19 Aug-07:43:35 Re: ferberite, pyrite, siderite, and..... ? (Jordi Fabre)

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
44987


The time now is Aug 21, 2018 03:42

Search for a textSearch for a text   

A general guide for using the Forum with some rules and tips
Identity or locality of this dense, spherulitic mineral?
  
  Index -> What is it? - Where is it from?
Like
1


View previous topic :: View next topic  
Author Message

Pete Modreski
Site Admin



Joined: 30 Jul 2007
Posts: 639
Location: Denver, Colorado


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Apr 19, 2018 14:35    Post subject: Identity or locality of this dense, spherulitic mineral?  

Dear Forum members, my turn again to try to ask for help with an identification question. This specimen was among a batch donated to a local group to be put in a silent auction or similar use. They showed it to me because it was unusually dense, and had no label with it--a bit of a puzzle.

It's an aggregate of spherulite-like masses, each around 5 mm in size. Some are nearly round, some have a somewhat blocky shape, where they are tightly grown together. They have a concentric, radiating internal structure. It's red-brown in color, and appears to have a hardness of about 5. One might describe it as looking somewhat waxy/translucent.

I measured the density by suspension in water, and got a specific gravity of 4.15 (which could be a bit low, since the mass has some interstices which may not fill with water when immersed). Here are two pictures.

Anyone have any ideas, or seen anything similar? My impression is that perhaps it is something in the apatite family, or perhaps, a pseudomorph of barite after chalcedony? [Does that ever occur?]

Thank you for any suggestions! --- Pete M.



20180419_123444.jpg
 Mineral: unknown
 Description:
Locality unknown
 Viewed:  1142 Time(s)

20180419_123444.jpg



20180419_123520.jpg
 Mineral: unknown
 Description:
Locality unknown
 Viewed:  1147 Time(s)

20180419_123520.jpg


Back to top
Reply to topic Reply with quote
Like
   

Bob Carnein




Joined: 22 Aug 2013
Posts: 116
Location: Florissant, CO

View user's profile

Send private message

PostPosted: Apr 19, 2018 15:11    Post subject: Re: Identity or locality of this dense, spherulitic mineral?  

Some barite from Sandoval Co., NM (sorry, I don't have a more exact locality) is radiating, nodular. As you said, low SG could result from impurities or spaces.
Back to top
Reply to topic Reply with quote
Like
   

Dale Hallmark




Joined: 16 Jun 2014
Posts: 171
Location: Texas Panhandle


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Apr 19, 2018 15:40    Post subject: Re: Identity or locality of this dense, spherulitic mineral?  

Looks like a poor grade of Rhodochrosite to me. But i am seldom right in these guess what it is questions.

Interesting looking though, whatever it is.

Dale
Back to top
Reply to topic Reply with quote
Like
1
   

Jordi Fabre
Overall coordinator of the Forum



Joined: 07 Aug 2006
Posts: 4119
Location: Barcelona


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Apr 20, 2018 16:35    Post subject: Re: Identity or locality of this dense, spherulitic mineral?  

Hi Pete,

Could you please check if it fizz in dilute HCl?

Regards

Jordi
Back to top
Reply to topic Reply with quote
Like
   

Pete Modreski
Site Admin



Joined: 30 Jul 2007
Posts: 639
Location: Denver, Colorado


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Apr 20, 2018 17:51    Post subject: Re: Identity or locality of this dense, spherulitic mineral?  

Thanks for asking this, Jordi, I should have reported this to begin with.

I just did a test with dilute HCl more carefully than I did before. A first, quick test had seemed to show, no fizzing. But, doing it more carefully, some places seem not to fizz, and some do, a bit. And when I crush some to a powder with the point of a knife, most of the powder fizzes a bit, but then it stops, and not all the powder has dissolved.

So, the material may be a mixture of more than one mineral, one a carbonate, the other not; or, a carbonate that is slowly and partially soluble in acid.

I had about convinced myself that this specimen is an example of a nodular-textured barite, such as what Bob Carnein had suggested. Now, perhaps, an intergrowth of... perhaps barite with some witherite, or some other carbonate?

I did also check, for the record, the specimen is not measurably radioactive.

(Being as it is just one specimen, of unknown locality, it's really not worth my trying to get XRD confirmation of the identity.)
Back to top
Reply to topic Reply with quote
Like
   

Bob Carnein




Joined: 22 Aug 2013
Posts: 116
Location: Florissant, CO

View user's profile

Send private message

PostPosted: Apr 20, 2018 18:23    Post subject: Re: Identity or locality of this dense, spherulitic mineral?  

Pete, can you do a flame test? That should give a greenish barium flame if witherite or baryte are present.
Back to top
Reply to topic Reply with quote
Like
   
Display posts from previous:   
   Index -> 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 2006-2018


Powered by FMF