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Identity HelpCan anybody help me to identify these beautiful rocks?

16th Jan 2020 11:44 UTCJORGE ESTRADA

I found them in a beach at Hong Kong.

16th Jan 2020 12:27 UTCLouis Zulli

The dark one appears to be a glass, either natural or man-made. At the moment, I'm leaning toward natural (obsidian), due to the faint suggestion of lithophysae in the image. Additional well-focused images of each specimen separately might help.

16th Jan 2020 13:04 UTCJORGE ESTRADA

Thanks Louis! Makes sense, for sure obsidian. Any guess for the clear one?

16th Jan 2020 12:56 UTCErik Vercammen Expert

The light one looks like quartz: if so, it should scratch glass.

16th Jan 2020 13:08 UTCJORGE ESTRADA

Thanks Erik! It is very hard, this rock can easily scratch glass, metal and even steel!

No bubbles inside, completely clear it takes whatever color is behind. Enhances light from a flashlight.

What about a Topaz?

16th Jan 2020 13:01 UTCJORGE ESTRADA

Here another angle!

16th Jan 2020 13:03 UTCJORGE ESTRADA

One more pic!

16th Jan 2020 14:49 UTCEd Clopton 🌟 Expert

The dark rock also could be a glassy slag. Obsidian seldom is that green in color.

Does the light one scratch quartz?

16th Jan 2020 16:29 UTCJORGE ESTRADA

I haven’t tried yet.

16th Jan 2020 15:08 UTCA. M.

Hardness of topaz is 8 - therefore it will scratch quartz.

16th Jan 2020 16:30 UTCJORGE ESTRADA

So, based just on the look, what would be your thought?

16th Jan 2020 18:33 UTCPaul Brandes 🌟 Manager

The dark one has the appearance of obsidian, but as Ed pointed out, obsidian rarely flashes that green in colour. By chance, do you happen to see any bubbles on or in it?

The light one could be quartz or topaz (or glass, seeing on where you found it...). One quick way to distinguish is measuring its specific gravity, if you are able to do so. Quartz is 2.65, topaz is around 3.5.

17th Jan 2020 03:08 UTCJORGE ESTRADA

Yes there are bubbles and kind of light olive/sandy grains inside.

It is translucent and a flashlight can be seen from side to side, even UV light.

16th Jan 2020 20:52 UTCMatthew Droppleman

I agree, not much else can be said until more data is provided. Please post about the results of the scratch test, for I am very curious!

17th Jan 2020 03:11 UTCJORGE ESTRADA

Thanks a lot Matt, Makes sense. I’ll try to run these scratch and gravity tests. Hopefully is something i can use to make a nice jewelry to my daughter.

17th Jan 2020 03:59 UTCPaul Brandes 🌟 Manager

Ok, the dark one is likely glass slag.

So now let's focus on the light one. Have you had a chance to check the specific gravity yet? Hardness would also be a good test to conduct.

19th Jan 2020 15:22 UTCGeorg Graf

My guess: The dark: glass slag. - The clear, white: Glass or Quartz. Topas has a
"perfect" cleavage, which one shoud realize on such a beach pebble.

20th Jan 2020 12:48 UTCJORGE ESTRADA

Thanks all for your feedback, so here are the conclusions:

Green one: 2.65

Clear one: 2.33

So Glass it is.

Until next time guys!!!

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