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Identity HelpHelp on identification of this mineral

30th Aug 2019 10:35 BSTDavid McNamara

09813170015671576566710.jpg
G'day All, 
Any ideas on this one?
Cheers Dave

30th Aug 2019 11:23 BSTKeith Compton Manager

David 

Please read the following message at the beginning of the Identity help forum.

30th Aug 2019 11:54 BSTDavid McNamara

Keith,
Sorry am new to this site and online identifications. 
there was no label with this specimen so I have no clue where it is from, I brought a box of mixed specimens and there is 8 of these. I have searched the Mindat data base thinking a type of Dolomite or Calcite but none of the photos match. 
The Crystals form multiple points finally terminating to a single tip. There is also some growth in a radiating pattern.
It is not very heavy,  the matrix appears to a type of basalt, 
Hope this helps
Dave

30th Aug 2019 18:13 BSTAndrew Debnam

Hi Keith, perhaps the link in your answer should be at the top or the body of the "start discussion in identity help"  thread saying read me first..
Andrew

30th Aug 2019 17:02 BSTDonald B Peck Expert

David,

Welcome to Mindat.   Place a drop or two of vinegar or dilute HCl on your specimen (in an unobtrusive spot.  And watch for bubbles to form or even rapid fizzing)  If you get bubbles you probably have calcite.  If there are none, it is probably quartz.   Try scratching (again in an unobtrusive spot) with a steel needle or knife tip and examine with a magnifier.  It it scratches, it is probably calcite (Hardness = 3 on Mohs Scale), if it doesn't, probably quartz (H=7) (Knife steel H= ca 5.5)  (From the photo, I am betting on quartz.  The orange color is from iron staining.)

Don

30th Aug 2019 19:17 BSTPaul Brandes Manager

Welcome to Mindat, David!

Agree with Don on all points. Appearance looks like quartz but, at the very least, a drop of vinegar/dilute HCl will be a big help here.

30th Aug 2019 20:46 BSTThomas Lühr Expert

Another vote for quartz

31st Aug 2019 01:34 BSTA. Mathauser

How about zeolite (maybe heulandite?)

31st Aug 2019 02:29 BSTJolyon Ralph Founder

could be

31st Aug 2019 13:01 BSTDebbie Woolf Manager

It looks familiar to me maybe N'Chwaning Calcite?

9th Sep 2019 13:25 BSTDavid McNamara

G'day Debbie. Just wondering about your comment of N'Chwaning Calcite. I have searched Mindat's pictures of Calcite from N'Chwaning and one really only looked similar which was Caboltian Calcite. A friend suggested Rhodocrisite, but again found nothing like it. I have a few specimens of this and well yeah really has me confused. Under magnification I count 6 sides to the crystals, to me it screams Calcite. Do you have ant pictures other than what is on Mindat?
Thank You in advance

1st Sep 2019 12:14 BSTHarold Moritz Expert

Stilbite.

9th Sep 2019 18:38 BSTDonald B Peck Expert

I  enlarged the photo as much as possible and I believe that A. Mathauser and Harold Moritz are correct.  The white crystals near the bottom of the photo definitely appear to be sheafs of stilbite.  The larger crystals near the top are out of focus and hard to determine . . . could be calcite or quartz.  Calcite is more probable (Did you test with vinegar or HCl?)
 
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