You are here:

Geology/specimen identification

Advertisement


Question
unknown specimen
unknown specimen  
My four year old son found this . Could you shed some light on what it might be?

Answer
This rock is quartz/chert with a pyrolusite coating. The rock itself is quartz/chert SiO2 the most common mineral on earth with minor amounts of iron (turning the quartz red). Quartz is clear with no tract minerals contained.  

Pyrolusite is a mineral consisting essentially of manganese dioxide (MnO2) and is important as an ore of manganese. It is a black, amorphous appearing mineral, often with a granular, fibrous or columnar structure, sometimes forming reniform crusts (your rock).  It has a metallic luster, a black or bluish-black streak, and readily soils the fingers. The specific gravity is about 4.8. Its name is from the Greek for fire and to wash, in reference to its use as a way to remove tints from glass. Pyrolusite is the mineral that coats much of the Inter-mountain west's cliffs and is called desert varnish. Pyrolusite is also found in botryoidal and dendritic habits.  

Geology

All Answers


Answers by Expert:


Ask Experts

Volunteer


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.

©2016 About.com. All rights reserved.