shermlock
has rocks in the head
Member since August 2011
Posts: 612
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Post by shermlock on Apr 23, 2012 20:03:21 GMT -5
I know I have some lapis, dumortierite and sodalite from estate sales but I'm starting to go cross eyed looking at this group. Is there an easy way for a novice to determine what rock/slab is dumortierite, which is sodalite and which is lapis? They all seem to look like each other to me.
Thanks, Scott
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Post by jakesrocks on Apr 23, 2012 20:13:52 GMT -5
Easiest way would be for you to post pics. We'll tell you which is which. Then just write on them with a Sharpie.
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Apr 24, 2012 8:22:57 GMT -5
google if you can not do photos Jim
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Post by tntmom on Apr 24, 2012 17:30:15 GMT -5
Hey Scott! Here is a couple of pictures if it will help. Unfortunately I do not have any slab pictures of Lapis. Lapis can vary greatly from almost solid blue to the tumbled Lapis rock that is shown below. My tumbled rock is considered low grade Lapis. It was very stable though and shined up great in a tumbler. High grade stuff though, I would never tumble and don't have any either.... As you can see they are all very blue but each stone has a distinct set of characteristics. Dumortierite: Sodalite: Lapis, low grade tumbled piece:
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Post by johnjsgems on Apr 24, 2012 18:40:30 GMT -5
Sodalite usually has black in the mix. Most lapis around is Afgan and will be shot through with gold flecks of pyrite. The CA desert dumortierite varies a lot but generally has a sparkly look and dark blue although I've seen a few blue/white pieces justifying the nickname "Desert Lapis".
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Post by jakesrocks on Apr 24, 2012 19:26:23 GMT -5
Hey John, I have some from the tailings of the old Black Jack silver mine that ranges from dark blue to lavender. Solid dumortierite usually has a radiating fibrous look under magnification.
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Post by johnjsgems on Apr 24, 2012 20:31:59 GMT -5
I've only collected at Indian Pass area in South East corner of CA. The stuff I found was really dark. I have some large pieces of very blue stuff in the yard my parents collected somewhere. All solid colored.
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Post by tntmom on Apr 24, 2012 20:41:09 GMT -5
I should clarify right now.... my slab that I pictured is Peruvian. I have no idea what the CA Dumortierite looks like? Sorry, hope I didn't cause unnecessary confusion?
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Post by helens on Apr 24, 2012 21:03:31 GMT -5
Here is Dumortierite from Tony, so I'm going to assume it's from the US... looks a lot like Krystees: Editing the pix below in so you can see them together: What I THOUGHT Chris said was Sodalite from Christopher1234 (could it Dumortite then?): Sodalite from Donnie (is this sodalite too??): Lapis from Donnie (is this lapis??):
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Post by jakesrocks on Apr 24, 2012 21:12:54 GMT -5
I'll see if I can dig out a couple cabs I kept, and get pics. In the Black Jack mine tailings, Dumortierite crystals can also be found. They're only druzy. Nothing big. Kind of rare to find crystals.
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Post by helens on Apr 24, 2012 21:34:50 GMT -5
Since we're all looking at ID'ing blue slabs... could you guys tell me what these blue ones are?? I thought this was Picasso marble... but after getting Tony's... I don't know what these are anymore (but they're awsome looking!). From Christopher1234 : Another unusual blue one from Christopher1234:
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Apr 25, 2012 2:05:32 GMT -5
Dumortierite has a Mohs hardness of 7 and a specific gravity of 3.3 to 3.4. It probably contains quartz (or it could be mostly quartz containing Dumortierite). Impure quartz has a specific gravity of about 2.6. It's pretty hard stuff, and if it's mostly Dumortierite, it's relatively heavy.
Lapis lazuli is 25% to 40% lazurite, the remainder being calcite, sodalite, and it usually contains pyrite. It has a Moh's hardness of 5.0 - 5.5 and a specific gravity of 2.7 - 2.9.
Sodalite has a Moh's hardness of 5.5 -6.0, and a specific gravity of 2.3. Harder than Lapis, not usually containing pyrite, but often with a lot of calcite. Without any calcite it's pretty light compared to Dumortierite. Calcite has a specific gravity of 2.7.
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Post by helens on Apr 25, 2012 3:57:34 GMT -5
Thanks Daniel, that helps a lot!
Any guesses on the last 2 slabs??
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Apr 25, 2012 16:29:18 GMT -5
The second to last looks like Sodalite to me. Is the white part easily scratched, i.e., Calcite, or is it Quartz? The last one looks like Dumortierite to me, but that varies a lot in color. Is it hard? Is that little bit of white quartz, or calcite? You should be able to recognize quartz with a hand lens. Is the brown iron oxide stained Quartz, or is it soft matrix, or might it be Pyrite?
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Post by jakesrocks on Apr 25, 2012 17:07:01 GMT -5
Not the best of pics, but these are dumortierite crystals from the tailings at the Black Jack Silver Mine, San Bernardino Co., Ca. Mounted on a broken pulley retrieved from the same tailings.
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Post by frane on Apr 29, 2012 20:59:04 GMT -5
Dumorterite is a quartz or silicate based material with a MOH of 7.0. It behaves differently from Sodalite or lapis. Sodalite has a high content of sodium (gets its name from that) and usually, but not always, is a royal blue color from the lazurite. It usually has white streaks that commonly are calcite but can surprise you with quartz at times. Sodalite can also be called swirlstone if it contains some hackmanite (pink areas).MOH of 5.5-6.0 Lapis lazulie, one of my favorites, is usually blue and the majority is from Afghanistan. Lighter varieties are from Columbia and I have heard that they mine some in NY. It contains the same properties as sodalite but will have the pyrite in it. From personal experience, I have found that sodalite can have undercutting and I did not have that same problem with Lapis. One thing is for sure, they both have a distinct sulfur smell to them when cabbing and at 5.0-5.5 it is the softest of the 3. Fran
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