Rosetta stone vs crazy lace

[rockjunquie]

These are nearly the same visually. Is Rosetta stone an agate or crazy lace? Dumb question, but it has bugged me a long time.

[captbob]

I often see "dolomite" in the same sentence with Rosetta.

Not so sure about that, but I've forgotten so much of what I once knew about rocks that it annoys me.

That Oaxaca Picture rock (wave jasper) is often called Rolling Hills dolomite, and there is Kona dolomite from Michigan, ... so MAYBE a dolomite?

Believe that the folks I bought a boat load of Rosetta from got it out of Durango Mexico.

[gemfeller]

All of these cabs were cut from material I bought in the late 1990s under the name of Rosetta Lace Agate. I’ve seen similar lace advertised under that name off and on since, but lately there’s another type of stone being marketed as Rosetta. I think it’s dolomite but I’ve never played with it.

As I understand it, Rosetta Lace Agate is from Mexico but it’s quite different than the old Crazylace. The colors tend toward orange and orange-red, some with occasional fine fortification patterns. There’s a lot of waste due to calcite inclusions.

[Sabre52]

Yeah, I have some big slabs and have cut some. Much softer than crazy lace agate and very much a calcite/dolomite type material with some quartz. Varies some in hardness throughout but probably about mohs 5 or so. All I have is the orange, red, white combo and only kind of resembles crazy lace in some parts of the slabs....Mel

[gemfeller]

Aug 14, 2017 16:09:23 GMT -5 Sabre52 said:

Yeah, I have some big slabs and have cut some. Much softer than crazy lace agate and very much a calcite/dolomite type material with some quartz. Varies some in hardness throughout but probably about mohs 5 or so. All I have is the orange, red, white combo and only kind of resembles crazy lace in some parts of the slabs....Mel

I know we disagreed on this once before but there's no dolomite in any of my material. Otherwise your description matches pretty closely but the hardness difference in mine is between the calcite and the very hard agate which is at least 7.5. Kingsley is currently selling what they call Rosetta Picture Rock and it looks identical to what I have. But trade names are crazy and are subject to periodic changes depending on the seller.

[rockjunquie]

I tried to find my slab and couldn't. It is harder than dolomite, I think. I do have a cab of it from a long time ago, though. Sorry, these are from when I set it. My slab is the same. Took a decent polish, but not hard like an agate.

[rockjunquie]

Just found this- www.etsystudio.com/listing/525265997/rosetta-stone-dolomite-lapidary-slab  looks the same as my cab and slab and they are calling it dolomite.

[rockjunquie]

I think Rick's cabs are whole different thing from I'm I'm talking about. The colors are brighter and the polish is much better. Plus, it just looks sharper.

[Sabre52]

I think what we may be seeing is the difference between dolomite the mineral and dolomite the rock. The rock can have variable amounts of quartz in it's composition so we may be seeing simply the same stone with greater or lesser amounts of quartz, with the hunks with more silica being much harder. I only have a couple of slabs left and they look real crazy lace like in part, but can be scratched with a knife blade in all parts which makes them probably about mohs 4-5. There are definitely quartz vugs which are in harder spots and calcite crystal vugs which are somewhat softer. More than likely a variation in hardness piece to piece or in hunks from different parts of a vein but all probably the same basic material.....Mel

[Deleted]

Aug 14, 2017 18:07:54 GMT -5 Sabre52 said:

I think what we may be seeing is the difference between dolomite the mineral and dolomite the rock. The rock can have variable amounts of quartz in it's composition so we may be seeing simply the same stone with greater or lesser amounts of quartz, with the hunks with more silica being much harder. I only have a couple of slabs left and they look real crazy lace like in part, but can be scratched with a knife blade in all parts which makes them probably about mohs 4-5. There are definitely quartz vugs which are in harder spots and calcite crystal vugs which are somewhat softer. More than likely a variation in hardness piece to piece or in hunks from different parts of a vein but all probably the same basic material.....Mel

Purely informational and nothing else.

Is dolomite a mineral? I thought dolomite was a mix of calcium and magnesium carbonates. No? A mix of two minerals? Feel free to kick my ass if I'm wrong!

[Sabre52]

No, I may be wrong but I think dolomite is a rock (common name) and a mineral. More properly probably should be dolomitic rock. That's the problem with common names. A combination of several minerals, including dolomite, the mineral makes dolomite, the rock. Dolomite crystals would be representative of the mineral dolomite in pure form. Mariposite for example is dolomitic marble and chrome green fuschite, but the dolomitic marble is actually dolomite the mineral and varying amounts of quartz. So most likely Rosetta Stone is a dolomitic rock containing the mineral dolomite, calcite and varying amounts of quartz which make it vary in hardness. But again, I ain't the best mineral guy in the world so I may be wrong too....Mel

[gemfeller]

Sticking my nose in here:

Any stone containing more than one mineral is a rock. Dolomite in its pure mineral form is crystalline, i.e,, hexagonal - rhombohedral. Colorless, white, pinkish or light tints; Luster glassy to pearly; Hardness 3.5-4, S.G. 2.8; Fracture conchoidal; Cleavage rhombohedral; brittle, transparent to translucent. I've seen faceted dolomite crysals.

Dolomite the rock (or dolostone as it's often called) resembles limestone but its chemistry has changed. The original calcium has been replaced by magnesium. It forms under the same conditions as limestone.

Credit to Dr. Frederick Pough.

It's important to distinguish between rocks and minerals. Lapis Lazuli, for instance, is a rock, not a mineral. It's usually composed of the minerals lazurite, calcite, sodalite and pyrite.

[jamesp]

I hope the younger generation is listening and maintains interest in this hobby.

[rmf]

Dolomite is CaMg(CO3)2 by definition a mineral.   There is also what Geologists would call dolostone which is mostly dolomite with other impurities.   Which is like limestone in that it is mostly CaCO3 the mineral calcite but with other stuff (mud, silt, etc) mixed in.   This is why some quarries are just selling gravel and some can sell high grade CaCO3 or CaMg(CO3)2 for specific uses.   Go into GNC and you can by dolomite pills and it is CaMg(CO3)2.   Or in the case of Tums high purity calcite.

[taylor]

The Etsy listing that rockjunquie referenced is mine. We purchased the material at the Tucson Gem show last year as "Rosetta stone." I had purchased a slab three years ago and at that time it was called Rosetta Dolomite. I kept the dolomite tag because the material is significantly softer than agate. It takes a nice polish, but one must work gently. At least 90%, if not all, of the material that vendor had was from Mexico. Sorry, but I don't know the composition of the rock.