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Geology/what kind of rock is this?


Side view
Side view  

Clear bubbly green
Clear bubbly green  
Will you help me identify this rock ? It seems like it was molten at one point then cooled rapidly. Volcanic or a meteor?It has an irredescence inside the pits that cover it .It has what may be olivine or peridot?green bubbly clearish glassy coating on one or two sides. It also is full of different size balls some silverish,some. Like rose gold or copper.Once I broke a portion off of it and it made a psssssh sound like release of gas and .it had a sulfur odor i think. It has a flat side .It is very slightly magnetic( barely moves a magnet on a string). Under magnification there are layers of black and red and green . Is it worth anything or is it rare?

Hi Sheri,
Again, I appreciate the additional description next to the pictures. Here is a very likely possibility. From your pictures it looks a volcanic rock called "vesicular basalt". Every now and then, these particular volcanics, which originate deeper down in the earth's crust bring up a gemmy visitor from the earth's upper mantle, in your case most likely a piece of the green mantle mineral Olivine (Fe,Mg)SiO4. Gem quality olivine is often traded as peridot (August's birth stone) among jewelers. If it is clear and void of fractures it can be faceted into a gem.
For a 1 carat peridot, prices range between $30 to $300, depending on quality. Here is a price estimator for you:
There is however sadly another possibility. You might have in your hand slag from green glass smelting. Slag is the waste product that is scrapped of smelting furnaces. It can look very pretty and without some further physical testing it is hard to tell. However, with the release of apparent sulfuric gas when broken, I am leaning right now more toward the volcanic origin of your specimen.
If you really want to know details, our university is offering free mineral analysis is an outreach while training our geoscientists. You would get a full several page report and yes, we would mail your sample back. Here is the FREE mineral ID info:
Hope this helps.  


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Uwe Richard Kackstaetter, Ph.D. (Dr.K)


I can answer questions concerning minerals, mineralogy, gems, metals, groundwater, national and international geoscience field trips and anything that has to do with geology. As a public service and part as training for new geoscientists, our university department provides detailed FREE mineral identification for individuals with available non-destructive and destructive analytical procedures and a several page report. Please contact me for details or go to for details..


I am a professor of applied geology and mineralogy with many hours of field experience. Furthermore, I enjoy recreational gold prospecting and mineral collecting. As a professor I am engaged in research concerning minerals, their identification and their occurrence. I am currently developing inexpensive, accurate mineral identification procedures to be used by experts and lay people alike.

Member of the GPAA (Gold Prospectors Association of America) as well as the Association of Environmental Geochemists. Member of the GSA (Geologic Society of America) Member of the AIPG (American Institute of Professional Geologists)

Here is a small sampling: Mineral-rock handbook: Rapid-easy mineral-rock determination : written for anyone interested in minerals and rocks - Proctor, Peterson, and Kackstaetter;Macmillan Pub. Co. (New York and Toronto and New York) Physical Geology Laboratory e-Manual with 20 Lab Exercises [now available for FREE]: Colorado Front Range Self-Guided Geology Field Trips [FREE download] Kackstaetter, U.R. (2014): A Rapid, Inexpensive and Portable Field and Laboratory Method to Accurately Determine the Specific Gravity of Rocks and Minerals. The Professional Geologist, Vol. 51, No.2, AIPG. Kackstaetter, U.R. (2014): SEDMIN - Microsoft Excel (TM) spreadsheet for calculating fine-grained sedimentary rock mineralogy from bulk geochemical analysis. Cent. Eur. J. Geosci. DOI: 10.2478/s13533-012-0170-3

Ph.D. in Applied Geology and Mineralogy. I am actively teaching courses in mineralogy, igneous & metamorphic petrology, applied volcanology and a variety of national and international field courses with mineral collecting opportunities. Background in precious metal exploration and groundwater (hydrogeology).

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