Stone(s) of the Day

MZ · **Posted:** Tue Apr 29, 2008 1:11 am

yes, i'm still looking and hoping to get my fix.........

movie zombie

Crystal Star · **Posted:** Tue Apr 29, 2008 3:02 pm

It's my understanding that the St Mary's River area of Southern Alberta Canada is not the only source, since the former squid-like creatures were quite abundant in all oceans worldwide, but the St Mary's region is the only area that produces enough gem quality material to make it financially viable . I've gotten some from other sources and the quality just isn't the same, and it makes me wonder if it's possibly from differences in the heat and pressure experienced by them in other locations, compared to the conditions that formed the gem quality ammolites found in Canada.

Xtreme1 · **Posted:** Tue Apr 29, 2008 7:39 pm

Thanks Crystal, Gem-n00b, Valeria102, Barbra, Spauwe & others for helping me to identify what I have

! We have Ammonite's all over around here, in linestone, quartz, granite ect.ect. I have several in my fossil collection that I found localy, some with mother of pearl or shell still left on them. I have never seen one like this until Spauwe gave me that link and there one was just like mine! I already knew it came from Madagascar, I was under the impression it was Ammolite covering the surface. Is it possible this is some kind of opalization as Gem-n00b was referring to?

gem-n00b · **Posted:** Tue Apr 29, 2008 8:14 pm

I don't know that there's a rigid distinction between "Ammolite" and "opalized Ammonite" except for the quality/locality. But then, I don't know much about Ammonites.

I don't think that people are saying that it's actually opal, as that would imply hydrated silica (SiO2·nH2O)... this stuff is (according to the GIA) "CaCO3 aragonite polymorph, with minor amounts of calcite, pyrite, silica, and other impurities". Both iridescent materials, but with different causes of iridescence.

Here's some pictures of "opalized Ammonite", not specimens of mine though.

Xtreme1 · **Posted:** Tue Apr 29, 2008 11:56 pm

Hey Karim,

The second photo is just like mine, with the banding and all

. So mine is opal as well

? I am very bad at photos still :cry:

, I am looking at the "Photography for dummies" at Office Max for $59.99

keyla · **Joined:** Tue Sep 12, 2006 7:56 pm **Posts:** 30

Love the ammonite photos, I wish I could get mine to come out anywhere close to that! *drools*

Has anyone here seen any ammonites with druzy formations on them? The one I have has patterning very similar to that in the first picture Karim posted, but has an orange druzy crystal coating over the entire end section as well. Just wondering if it's something that happens fairly frequently, and what it might be...

gem-n00b · **Posted:** Wed Apr 30, 2008 3:42 pm

Druzy crystals (calcite, I believe most commonly) seem to form in many of the inner chambers. This is only usually seen if the Ammonites are sliced lengthwise. Here's a photo, is that what you're talking about?

Usually many/most of the chambers are filled up with "cement"... just an ugly gray/brown/red rock. To find specimens where all the chambers are crystalized is special indeed.

This one here is pretty good but still a bit shy of perfect.

Picture removed; size over acceptable limits

If you want the ultimate in cool/exotic gems (with the possible exception of extraterrestrial peridot) how about finding a nice chunk of calcite in an Ammonite that's facet grade and having it cut?

gem-n00b · **Posted:** Wed Apr 30, 2008 3:45 pm

The pattern on the outside of the shell is commonly referred to as "sutures". A Google search for "ammonite suture" should bring up information as to why the structures are there. Here's a photo of some exceptionally fine suturing. The only downside is that it's usually an "either or" with iridescence and sutures. The sutures are under the shell and the iridescence is in the shell... this is visible in that top "opalized" photo. Exceptions can occur with very thin layers of shell remaining, at least as I recall.

keyla · **Joined:** Tue Sep 12, 2006 7:56 pm **Posts:** 30

Not that it's a good picture by any means, but here's the crystal formation I was referring to. If you look closely, there are itty bitty teeny orange crystals hiding at the rough edge.

Picture removed; format over acceptible limits

I'm not brave enough to cut this in half and see what I get!

gem-n00b · **Posted:** Thu May 01, 2008 11:32 am

Yup, that's the same stuff. In your case it's the "outermost" chamber (at least) that got the crystals growing in it. Likely, there are more of those inside. But that's no reason to chop the thing in half! If you like it as is, I say leave it!

I will say this though... in my experience it is rare for that last (outermost) chamber to be crystalized... that might argue for crystals in all the chambers.

One internet (eBay) seller of Ammonites and other fossils consistently has great photos of the items. I am not vouching for the seller (no experience with him/her), but I always enjoy browsing the images.

http://stores.ebay.com/British-Jurassic-Fossils-Retail

JLWhite · **Posted:** Fri May 02, 2008 10:46 am

Ammonites are very cool indeed. Saw a ton of them at this year's Tucson Show. Some were VERY large (around 2 feet across) and wonderfully irridescent. I have always been intrigued with fossils and with gems, so this is the best of both worlds

ELVIS PRASIOLITE · **Posted:** Fri May 02, 2008 11:31 am

Cool thread!

Rocka hula Red Zircon!

http://www.ajsgems.com/cpage/products/d ... C-5KORhPKm

ELVIS PRASIOLITE · **Posted:** Sat May 03, 2008 1:36 pm

Rockahula! Uraguay Amethyst, 54.80 cts!

http://www.moregems.com/products/amethy ... 80cts.html

collinan · **Joined:** Mon Feb 25, 2008 4:33 pm **Posts:** 83

Wow, that is a very impressing Amethyst!

Alberto · **Posted:** Sun May 04, 2008 11:00 am

and, but it's a personal opinion, Uruguay stones are the best.
ciao
alberto

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