Testing mineral properites?

The format of minerals in the database contains some physical/chemical properties, but a section on actually testing the mineral using those properties would be highly useful. The old Dana's System was unique in the type of tests suggested and outcomes for different tests. Any possibility of adding such information to the database?

Henry Barwood

It was proposed for the last upgrade of the mineral section and was greeted with deafening silence. Main problem would be to find time/someone to enter the data.

Yes, I supose there are not too many descriptive mineralogists around any more. Back when I first got started with minerals, we would run all sorts of tests to confirm the identity of a specimen. Very few people tend to do that these days.

Henry

Henry:

I'd love to be able to run in depth tests myself. Unfortunatly I don't have access to any facilities and if I did, I don't have the skills to use them.

IMHO, methods are too numerous. But a list of the latter (without going into the particularities of the best method applied to one given mineral) would perhaps be of some help to the lay(wo)men. Examples: transmitted pol. light, reflected light, spot tests, surface coloration, bead and flame tests, UV, radioactivity,... From there on, one could be directed to a more descriptive book or paper (Example: Short: Determin. of ore minerals. USGS Bull. 914). I am probably day-dreaming, in those times of XRD and EMP.

I am heavily into determinative mineralogy. And, Jenna, it is not that difficult to learn nor does it take skills that cannot be mastered.

I use the common physical properties (including specific gravity), chemical spot tests, and occasionally optical properties. A simple specific gravity balance that is quite accurate and precise can be built. An ordinary used student biological microscope can be modified to *almost* do the work of a petrographic scope.

I am a micromounter, and testing minerals is,to me, a lot more interesting than simply gluing a specimen on a peg and then in a small box.

At ten yrs old, my father gave me a can of rocks, a copy of Pough's handbook, and a Gilbert chemistry set (it even had a blowpipe!) and gave a table out in the shed....I've been in the "lab" ever since...Donald is right...the skills needed are NOT difficult and the rewards are great! Any local used bookstore will have copies of the older determinitive mineralogy textbooks and the older texts devote MUCH more print to techniques than later texts....my most dog-eared and worn is Brush & Penfield's text on beads & blowpipe. As did Donald, I modified an old brass-tube biological 'scope (added substage & tube polarizers & rotating stage) which was adequate until I could afford a REAL petrographic 'scope. dig in...it's as much fun as being on the outcrop!!!

Hi Jenna,

Some simple techniques/procedures rarely used these days:

Blowpipe (bead) analysis (very simple tools needed)

Ring oven (more complex, but still easy to do with a little knowledge of chemistry)

Specific gravity (heavy liquid technique)

Acid reaction

Charcoal and plaster block tests (usually combined with blowpipe analysis)

Refractive index (OK, you need a scope and some oils, but still pretty simple)

The amateur who has mastered these simple techniques can probably identify 80-90% of the mineral species. Notice that I didn't mention X-ray or microprobes of any kind.

Curt Segeler used to routinely chemically analyze samples with a ring oven before sending them to me to confirm with XRD. In a decade, he only missed a common mineral once, and it was a metamict zircon that would have fooled most people!

"The amateur who has mastered these simple techniques can probably identify 80-90% of the mineral species."

I seriously doubt that (unless "mineral species" is restricted to the most common minerals and includes families and groups instead of single species).


I would also highly recommend microchemical spot tests (applicable mainly to non-silicates / secondary minerals) - they worked fine for me when I was a student.

My old copy of the Audabon Society Rocks and Minerals guide had a listing of bead tests, test tube tests, etc. for many of the samples they listed.

Curt learned and used the spindle stage technique for deteriming the refractive indices, and microchemical reagents for qualitative chem testing. I spent many hours at his home working on unknowns from various people. We did (self-)publish in the early 80's(?) a determinative table for pegmatite phosphates that included microchemical tests and optical data. It badly needs updating, but I should have a copy around somewhere...

I, too, spent many hours at Curt Segelr's home. He was a generous teacher. He taught me to use the ring furnace and the spindle stage. I built both of them and while I don't use the ring furnace a lot (I tend to use simple spot tests), I think the spindle stage is probably the single most powerful tool that the amateur mineralogist can use.

Donald Bloss and his students developed the spindle stage techniques and produced a computer program, EXCALIBR, which does all the hard work. It has gone through several generations and the latest EXCALIBR-W is available free. There is an article in "The Microscope" by Mickey Gunter that tells how to use the spindle stage and what it can do. For anyone interested, both the article and EXCALIBR-W (download) are available on his website at (Univ of Idaho).

Perhaps I was a bit optimistic about identifying minerals; however, outside the groups (like amphiboles) where even the professional mineralogists fear to tread, why would it not be possible to identify a mineral based on physical properties, optical properties and chemistry? Have we become so linked to our equipment that we cannot identify a mineral without single crystal data?

Don't forget that microprobes/SEM are also indispensible. I think that most advanced micromounters do a very good ID without expensive equipment (if for no other reason than it would be very expensive to get everything tested). These people supply professionals with about half of the new minerals described every year. I also have seen Don work his magic on a mineral ID table at local shows.

Some general articles on testing minerals would be useful, but I don't think there should be a testing section listed under each mineral individually. Firstly, that would get very repetitive (Do we want to describe the flame test for Sr under each Sr-bearing species?). Secondly, the tests that could be applied to any given problem vary enormously depending on factors like: Is the mineral an isolated grain or still attached to matrix? Is it transparent enough for optical tests? What impurities is it associated with? What elemental substitutions are possible? How big is the grain, or how much material is available to sacrifice? What equipment and chemicals does the user have access to? A large book could be written on this topic (perhaps downloadable from Mindat books?), but to include even the basics under each mineral description is simply something that will never get done, given the limits of our volunteer labour force.

In our largest local used bookstore there is, in the geology area,a section of mineralogy texts at least 5ft long containing 8 or 9 determinitive mineralogy texts...most priced under $12.00. These range in date of publication or revision from the 1890's to the mid-1940's. With so much data already available why should mindat waste precious storage (and volunteer's time). And, yes, modern techniques are necessary tools - xrd, xrf, ramen spec.,etc, but many of the minerals presented in the "identity Help" forum could be quickly ID'ed with minimal expertise if a text w/ tables wwere available.

In second-hand bookshops round here, you'll be fortunate to find ANYTHING to do with geology, let alone special interests such as mining, mineralogy or petrology. Books on crystal "healing" and astrology are unfortunately far more abundant; a sad sign of the times.

Pete N.

My primary mineral identification book at the moment "Minerals: Identifying, classifying, and collecting them" by Rupert Hochleitner, I was fortunate enough to find at a used book sale at school for $5

It's not the most comprehensive but it's a neat little book, especially for the price I got it at, and it even has some Greenland minerals in it

Don, I enjoyed your reference to Curt's teaching you how to use the spindle stage. And also your recognition that the spindle stage plus my program EXCALIBR does all the hard work for you. I remember Curt being in the first workshop I taught on the spindle stage. I'm so glad he passed the info to you. You're right, the spindle stage (+ EXCALIBR) is the most powerful, relatively inexpensive device at the disposal of a mineralogist for studying transparent crystals.
At 92 I've just finished my memoir which the Mineralogical Society of America will publish.
My regards to Henry.
Don Bloss

Don,

Thank you for your response. I am continuously amazed at the ease of use and the forgiving nature of the spindle stage. I find that the most difficult part of using it is mounting a grain in a position that is useful. Thank you for your contributions to the science.

Don Peck