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Identity HelpHelp with identification

4th Sep 2014 01:42 UTCMike Punt

I posted this pic on a geology website and didn't get any help. They directed me here so I'm hoping someone knows what these are.

My parents brought home some rocks for my daughter from Jamaica. If anyone could let me know what they are, I'd appreciate it. I think the top two are different from the bottom two. The white lines on the upper two turn blue when wet as evidenced by the upper right rock. The bottom two do not change color.

Thanks

4th Sep 2014 03:15 UTCBill Cordua 🌟 Manager

Hi Mike,

The photos are a bit blurry - which makes it a bit tricky and I'll suggest a few things to test. They all look like a rock called breccia - a rock made of angular fragments of other rocks. These form when, say, a fault breaks up rocks, moves them around and then re-cements them with chemicals in fluids moving up or down the fault. . The light veins are part of the cement. Commonly these are quartz or calcite - although the change in color of the one suggests perhaps opal. I'd try checking their hardness- are the white veins harder or softer than glass? If harder, likely quartz. Softer suggests calcite. Calcite will bubble (release carbon dioxide bubbles) if you hit with a drop of weak acid - hydrochloric will preferred, but vinegar will work, although you may need a powder to see it work. Opal's hardness is not much greater than glass.

4th Sep 2014 03:48 UTCDoug Daniels

Also try scratching the veins and the surrounding material with a knife (a good one, not a butter knife). Are they scratched, or not?

5th Sep 2014 00:00 UTCPaul Brandes 🌟 Manager

First off, welcome to Mindat Mike.

Before anyone can make an educated guess as to what these are, you're going to have to do some basic testing (hardness, streak, acid drop, etc.) first so that we have something to go on. With that said, I believe I see some conchoidal fracture in the upper left specimen, which suggests a microcrystalline quartz. You may also want to ask your parents where on Jamaica they found these; that could make it easier to identify as well.

5th Sep 2014 00:22 UTCMike Punt

Ok, so I scratched the veins on both types. The white on the lower two is very hard. The white (the part that turned blue when wet) on the upper two rocks seemed very soft when scratched. The tip of the knife went in very easily and sort of made a powder when scratched. The darker color material on each type is very hard. I'm not sure this helps in any way. Unfortunately, I don't have any test kits or acid to go further at the moment.

It was Negril, Jamaica.

I guess I'm trying to figure out if these are just ordinary rocks aside from being interesting to me.

Thanks

5th Sep 2014 03:02 UTCBill Cordua 🌟 Manager

You are doing great Mike. You successfully did 2 very important hardness tests. The white is very likely some form of quartz (either macrocrystalline or microcrystalline). The light stuff that turns blue when wet is - intriguing! Perhaps its some form of clay mineral. Does it get sticky when you wet it?

As to if these rocks are "ordinary" - well, every rock is different and all of them have some interesting history of the earth's past to tell us. These were probably crunched up along a fault, which I think is pretty cool. And it's from a neat place and was a gift somebody special found and given to somebody special. I have rocks in my collection collected for me by my Grandmother and my brother, which make them very special to me. I'll never get rid of them. I'd say yours commercially aren't likely very valuable, but if you and your daughter like them, who cares?

5th Sep 2014 15:02 UTCMike Punt

Bill Cordua Wrote:

-------------------------------------------------------

> You are doing great Mike. You successfully did 2

> very important hardness tests. The white is very

> likely some form of quartz (either

> macrocrystalline or microcrystalline). The light

> stuff that turns blue when wet is - intriguing!

> Perhaps its some form of clay mineral. Does it get

> sticky when you wet it?

>

> As to if these rocks are "ordinary" - well, every

> rock is different and all of them have some

> interesting history of the earth's past to tell

> us. These were probably crunched up along a fault,

> which I think is pretty cool. And it's from a

> neat place and was a gift somebody special found

> and given to somebody special. I have rocks in my

> collection collected for me by my Grandmother and

> my brother, which make them very special to me.

> I'll never get rid of them. I'd say yours

> commercially aren't likely very valuable, but if

> you and your daughter like them, who cares?

Just to be clear, the white lines (veins) are what turn blue on the top two rocks. The bottom two (the rocks with the harder white material) do no change color at all. The reason my dad thought the top two were interesting was that he found them in the ocean and the lines were blue. When he got them home and took them out of the luggage they were now white since they dried out.

I just wet one of the top two again and the veins that turned blue seem a bit slimier than when dry. I would not say it was sticky at all. So are you still leaning towards quartz or was that only referring to the harder material on the bottom two?

I can take better images if anyone thinks it would help. I would love to know why the color changes.

Yes Bill, I'm not trying to get a value on these as I know they are just rocks, but we think they are very interesting and just trying to get more info and facts about them.

Thanks!!!

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