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Is This Prehnite and Calcite or Hemimorphite or Something Else?

Posted by Deanna Kane  
Deanna Kane April 17, 2018 01:19AM
Hi again.

I know I've been probably annoying all of you lately with all my requests for identifications, but hopefully you guys aren't too sick of me yet, LOL

I just got this big, heavy 6 inch by 6 inch specimen. The person I bought it from is not a mineral collector and was just selling it for $3 so I had to have it for that awesome price. It had a very old yellowed label on it that said Phrenite or Hemimorphite with calcite.

I know many of you advance collectors are groaning and rolling your eyes by now. Inside your heads you are shouting, "stop collecting pieces that aren't labeled with location or identification", but like I said earlier for $3, I couldn't resist because it was pretty.

Any ideas what the heck this could be?

More pictures to follow...

Sorry in advance, but this post is picture heavy, LOL

Edited 2 time(s). Last edit at 04/26/2018 08:45AM by Keith Compton.
Deanna Kane April 17, 2018 01:21AM

Deanna Kane April 17, 2018 01:23AM

Deanna Kane April 17, 2018 01:25AM

Deanna Kane April 17, 2018 01:27AM

Deanna Kane April 17, 2018 01:29AM

Deanna Kane April 17, 2018 01:31AM

Alfredo Petrov April 17, 2018 01:37AM
Looks like prehnite.
Deanna Kane April 17, 2018 01:40AM
Alfredo, thanks for your reply. I want to put a label on it and this info really helps me.
Erin Delventhal April 17, 2018 01:56AM
Whatever it is, it looks like it needs a bath.

Completely off topic to your question here, but as some advice to a burgeoning collector, I'd recommend that you consider investing in an ultrasonic machine, which is a very effective and mineral-friendly way of cleaning your specimens.
Deanna Kane April 17, 2018 02:07AM
Erin, I'm laughing right now. I was so proud of my efforts when I cleaned it today. I thought it was gleaming when I was through. I guess I utterly failed, lol. I spent 20 minutes with a soft toothbrush, scrubbing and washing it with dawn dish washing detergent and rinsed it really well. Usually when I do this, I can see filth and dirt go down the drain. This time, I saw none. I guess I will be buying one of those ultrasonic machines ; )

Edited 2 time(s). Last edit at 04/17/2018 02:23AM by Deanna Kane.
Deanna Kane April 17, 2018 02:09AM
BTW, Erin I can't get those grayish/black, burnt looking speckles off of it no matter how hard I tried. I think it might be a mineral and not dirt.

Edited 2 time(s). Last edit at 04/17/2018 02:22AM by Deanna Kane.
Deanna Kane April 17, 2018 02:16AM
Maybe what looks like dirt could be goethite?
Deanna Kane April 17, 2018 02:27AM
Hi again Erin,
I just put my spotlight on it and got my jeweler's loop out. I really think what looks like dirt is definitely a mineral.

The best I can describe it is it reminds me of a toy I had as a child. It was a picture of a bald guy encased in plastic with iron/metallic particles and you took a magnet and moved them around to give the bald guy hair, a beard and a mustache. It looks like those little magnetic particles up close. Sorry if my analogy was ridiculous, but this is all I can think of right now to describe it, lol.

Edited 1 time(s). Last edit at 04/17/2018 02:28AM by Deanna Kane.
Alfredo Petrov April 17, 2018 02:46AM
Deanna, those fuzzy black crusts could be manganese oxides, in which case they will dissolve away in acidified hydrogen peroxide. Take a bottle of hydrogen peroxide solution from the drugstore and add a little hydrochloric acid (the stuff sold for swimming pools is fine), about a fifth of the volume of hydrogen peroxide, or even less, and let it soak for a few minutes.

Weaker acid is better, because if it's too strong, or you leave it in too long, it will hurt the luster of the prehnite and zeolites. A better method might be to just leave as is and enjoy the contrast the black spots give it. ;))

Edited 2 time(s). Last edit at 04/17/2018 02:50AM by Alfredo Petrov.
Erin Delventhal April 17, 2018 03:13AM
For what it's worth, my ultrasonic tends to take off schmutz (a mineral technical term you should become familiar with) much better than a toothbrush.

However, I'm not insisting that the black material needs to be removed, especially if it's mineralized - though Alfredo's suggestion as to how to do so is fair, as is the suggestion of just enjoying it as it is.

Outside of all of that, I still think you'd benefit from having an ultrasonic.
A. Mathauser April 17, 2018 03:15AM
It's look like green prehnite, clear-white calcite and elongated small white laumontite, probably from Paterson, Passaic County, New Jersey.

Edited 1 time(s). Last edit at 04/17/2018 03:17AM by A. Mathauser.
Deanna Kane April 17, 2018 03:19AM
Hi Erin and Alfredo. Thanks so much for the wonderful and very helpful tips. I will look to get an ultrasonic machine. For now, I'm going to leave the black schmutz on until I get better educated on minerals. However, if it is an actual mineral, I think I will leave it be. For some stupid reason I would feel guilty for removing it because if it was there for millions of years, I guess I feel I shouldn't erase a part of nature. Yes, I'm a sentimental fool, lol.
Deanna Kane April 17, 2018 05:10AM
Thanks A.
I appreciate that information very much : )
Alfred L. Ostrander April 17, 2018 01:36PM

Just be careful with an ultrasonic cleaner. Fragile specimens can end up as a pile of debris at the bottom of the tank.
Erin Delventhal April 17, 2018 02:25PM

Would those fragile specimens be better off subjected to a toothbrush?
I've had no issues with delicate specimens in my ultrasonic, so I'm curious what you're referring to.

Donald B Peck April 17, 2018 03:14PM
Deanna, "stop collecting pieces that aren't labeled with location or identification" LOL

I think A. Mathouser nailed it. The small lath like xls that are scattered over the green prehnite look to be laumontite. Possibly from the Paterson, NJ area (it is typical}.

Alfred L. Ostrander April 17, 2018 06:27PM

Can't say I'm too hot on starting out by scrubbing away with a toothbrush either. Maybe someday you will find out what I mean when you find a bit of debris at the bottom of your ultrasonic tank as the result of putting the wrong thing in an ultrasonic. I can say the same thing about cleaning certain minerals with high pressure sprays. Works for some things, highly destructive for others.

Solubility is important. Friability is major. Porous matrix needs considered. Type of matrix needs to be considered.

Keep in mind that an ultrasonic is vibrating a bit vigorously. Sometimes too much for specimens. Even an insoluble crystal can be vibrated off the matrix.

Just forty some years of experience speaking here.
Gregg Little April 17, 2018 10:22PM
A. Mathouser and Don;

I thought laumontite was susceptible to dehydration and ending up as a crumbing mess in the specimen tray. Also, if we are talking about the same fine acicular crystals, they appear to have a semi-transparent look to them. All the laumonite in my collection has crumbed and is not in the least translucent. I also can't consistently see any of those obvious "chisel-like" terminations. Am I missing something? I don't really have any other suggestions other than may be heulandite?
Donald B Peck April 18, 2018 12:26AM
I had specimens from the New Street Quarry in Paterson, NJ that looked exactly like Deanna's. The specimens were kept in my basement, which admittedly, was a bit humid and the laumontite seemed to be stable. I can say that all(?) the crystals were pretty much opaque white.
A. Mathauser April 18, 2018 01:21AM
Gregg, you are correct. If you spray with - for example - hairspray, laumontite is fairy stable. If you don't - it changes, it's really leonhardite and sadly, in time, crumbles... I have seen many specimens with this.
Stephen C. Blyskal April 26, 2018 02:17AM
Based on the photographs, the main mineral is definitely prehnite and some of it is pretty good quality. The backside of the specimen showing the matrix is definitely weathered basalt. I also saw modified rhombohedral calcite crystals in one photo. The white or clear crystals are either laumontite or natrolite. This specimen is from Prospect Park Quarry in Prospect Park, NJ or Upper New St Quarry in Paterson, NJ. I have several similar to this. Do not clean any more with a toothbrush or you will end up removing the white crystals. Same with acid or an ultrasonic. I don't think you need to do anything more to this specimen except enjoy it. The coatings on the prehnite will not come off with ordinary means. Maybe an air abrasive.
Glen Gruber (2) April 26, 2018 06:43AM
From the pic's it's Prehnite and the dark black spots ect.... could be epidote as basalt minerals go it looks like you some fine delicate crystation I think unless it's clay you risk damage to finer smaller features of this piece with more cleaning. Also using a toothbrush is a bit rough try a makeup brush or one with fine thick bristles. Nice piece...
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