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Geology/Minerals identification help please


Rock 1
Rock 1  

Rock 2
Rock 2  
Hi. I live near Hattiesburg, Mississippi. I was hoping you could help me identify our rock for my grandson's mineral collection. Thanks for your time!

While identification from pictures is always a little tricky, I can tell you that your rock specimen is most likely an igneous rock. These type of rocks are created from previously molten material. Igneous rocks form on the surface by volcanic eruptions. When lava cools, it forms a very fine grained igneous rock, such as lava rock.
However, molten material can also be stuck underground and never make it to the surface. As it cools very slowly underground it will turn into an igneous rock that is very coarse grained with visible mineral grains. These are called plutonic igneous rocks. Your specimen is most likely such a plutonic igneous rock with an added special quality. The crystals or minerals in it a very large and of a certain composition. Such an igneous rock is called a Pegmatite, a very coarse grained, usually granitic type rock, with sometimes extremely large crystals.
The clear to milky material in your specimen is most likely the mineral quartz (SiO2), which is very common. If you see any small silvery flakes in your sample, these are Muscovite mica (KAl2(AlSi3O10)(F,OH)2). The blackish material is hard to distinguish from the picture. Possibilities are the mineral magnetite (Fe3O4) (see if a magnet sticks to it), or it could be hornblende ((Ca,Na)23(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2), this is what I assume the larger black blob might be, or it could be black tourmaline, also known as schorl (Na(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)), especially if it has an hexagonal outline, or if it is flaky it could be the black mica Biotite (K(Mg,Fe)3AlSi3O10(OH)2), or a combination of these minerals.
However, in general, the State of Mississippi is not known for actual large outcrops of plutonic igneous rocks. Thus your specimen is most likely a "transplant" from a distant area, arriving in Mississippi through ice transport during the last ice age.  


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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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