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Geology/type of rock

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Question
rocks
rocks  
hi there, i was wondering if you can look at these 2 pictures ive attached to
this message  and maybe be able to tell me a lil something about them. they are
extremely heavy especially the one that looks burned and they are both magnetic,
any info you can give me would be highly appreciated. and thanks for your time

Answer
I only got one picture and the rock/mineral which looks very much like Magnetite.  Magnetite is a mineral, one of the three common naturally occurring iron oxides (chemical formula Fe3O4) and a member of the spinel group. Magnetite is the most magnetic of all the naturally occurring minerals on Earth. Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, and this was how ancient people first noticed the property of magnetism.  Below are the characteristics of magnetite.

Color   Black, gray with brownish tint in reflected sun
Crystal habit   Octahedral, fine granular to massive
Crystal system   Isometric Hexoctahedral
Twinning   On {Ill} as both twin and composition plane, the spinel law, as contact twins
Cleavage   Indistinct, parting on {Ill}, very good
Fracture   Uneven
Tenacity   Brittle
Mohs scale of hardness   5.56.5
Luster   Metallic
Streak   (when scrapped on a porcelain plate) Black
Diaphaneity   Opaque
Specific gravity   5.175.18
Solubility   Dissolves slowly in hydrochloric acid

You might try some of the above to make sure that the rock(s) are magnetite.  For reference a sandstone of limestone has a specific gravity of about 2.65 as opposed to Magnetite at 5.17.  Hardness and be checked by a knife blade at about 5 - 5.5 (when you scratch the rock with a knife it should not leave a mark.  High grade magnetite if the deposit is large enough and near enough to a railroad or navigable river has value.

Small grains of magnetite occur in almost all igneous and metamorphic rocks.  

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Joe Norris

Expertise

I am an economic geologist. An economic geologist does mineral evaluations and appraisals of mineral or mining properties. I can tell you if your deposit has value - remember that a mineral deposit, no matter how good, only has value when mined. Any value assigned to a mineral deposit, in the ground, is only the speculative value that deposit.

Experience

I have been a economic geologist for most of my 35 year career. Although I have done work in perhaps 45 states and numerious countries much of my work has been in Appalachian coal, intermountain west gold and silver, and Arizona uranium.

Organizations
Past President of the Virginia Section of the American Institute of Professional Geologists and a certified geologist in twelve states.

Education/Credentials
BS Degree from Eastern Kentucky University. Work on MS Degree @ Eastern Kentucky University, Colorad School of Mines & Marshall University Numerious short courses on the value of mineral deposits and how to value same. Also several short courses dealing with the different types of geologic processes; sedimentary, igneous, metamorphic along with the mineral associated with each.

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