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Identity HelpMineral Identification (How to - PLEASE READ before posting questions)

4th Mar 2006 16:13 UTCAlan Plante




QUERY CHECKLIST


It will help a great deal if someone submitting a "What is it?" query use the following checklist to gather as much information as possible to post with your query. If you are unfamiliar with making the observations and simple tests required, use the Mineral Identification Key at "minsocam.org." It tells you how to make the obeservations and tests, and takes you through the ID processes in a step-by-step fashion.


Do not assume that a photo posted with your query answers questions about luster - and even color in some cases. State these characteristics even when you are submitting a photo.


- What "luster" does the mineral have? - Luster

- What color is the mineral?

- What color is the "streak" of the mineral?

- What is the mineral's "hardness"? - Hardness

- What are the dimensions of the specimen? Or of a given crystal on a specimen?

- What locality did the specimen come from? (This could be extremely important, so don't forget to state it if you know.)

- What other minerals are found on the specimen besides the one you are asking to be identified?


Some additional information that will be helpful includes:


- What shape is(are) the crystal(s)? (If you can state which Crystal System they belong to - such as "Isometric" or "Hexagonal" - it will help a lot.)

- What is the "specific gravity" of the mineral? - Specific Gravity

- Does a small chip of the mineral react in a drop of acid? or not? (If you do an acid test, report what acid you used and at what strength - not just the results of the test.)


When submitting a photo, do the following first:


-Take the photo and the specimen outside on a sunny day and compare them. Does the photo look like the specimen? - Sharp focus? Well lit? Colors true?


If your photo does not look like the mineral - blurry, or dark, or color not right - then it will not help in the mineral's identification. (Even a good photo may not help - so a poor one will be less than useless...)

Further suggestions about taking photos that you submit to the forum. No matter how many times we plead for photos that are in focus people continue to send in out of focus images. Please check your images before sending them, and if they are not in focus. If there is any doubt, just attach the image to an email and send it to yourself. If the Image is not in focus, don't send them, but rather retake the image till you learn to take sharp in focus images. When you submit an image to this forum you often engage the attention of some of the most knowledgeable and experienced mineral people in the world. Common courtesy should dictate that you do not waist their time. If I take a look at a blurry image in an Identity Help posting I will frequently just click on to the next post and not waist my time trying to help the person. If you images are sharp and in focus, you will get much better help than you will if you submit an out of focus image.


Also, take a picture of the specimen in natural lighting, preferably in sunlight and avoid lighting where the spectral values are skewed like fluorescent lighting or tungsten filament light. Take the picture on a neutral colored background or with a background. Do not take the picture on a black background. Leave the art photos to Hollywood. A white or gray or tan background is OK. Even your hand is OK. Put some sort of scale in the image like your hand, a coin or a ruler. Do not take a picture of the specimen when wet! Or if you just have to to make the colors pop, include at least one in its dry state. Do not send just an image of a closeup part of the specimen. Close ups are OK, and sometimes very necessary, but include at least one image of the entire specimen.> Rock Currier 2010 (I hope Alan will tolerate this addition).


DO NOT ASSUME THAT A PHOTO IS ALL YOU NEED TO SUBMITT! Minerals can be difficult to identify when they are right in the person's hand or lab - never mind at intermess-reach in a photo. A photo is almost NEVER enough to identify a mineral from. In order to give the people who help you the best shot possible at identifying your mystery mineral for you, do your best to answer all the question on the checklist above before you post your query here - and then include ALL the information you gathered in your query.


Doing the above won't always get you a positive identification, but it will certainly be much more like to than posting a photo and asking "What is it?"


KOR!


Alan

16th Feb 2006 16:56 UTCDavid Von Bargen Manager

Below are some comments about information, that when included with your question, can greatly increase the probability that you can be given a correct identification of your unknowns.


DVB


This is posted in general response to a few rather vague and hopeful posts asking for identification of an unknown mineral, where it would have been much more likely that others would be able to give helpful answers if some more indication of a few basic physical properties had been given. An out-of-focus photo with only a "what's this?" message, or a description like "it's soft and white" won't be likely to get much positive response.


Below are some of the features that anyone trying to identify a mineral specimen without any laboratory facilities or specialist test instruments should try to characterise. In many cases, not all of these may be observed confidently, but even a few of them will start to narrow the possibilities rapidly.


What is the "lustre" - metallic, resinous, pearly, glassy etc. and is it highly reflective or dull? Is there any surface tarnish? Not only it's colour, but it's transparency. If it is opaque or if almost opaque, can you see any light through thin edges, and if so what colour is the transmitted light? Hardness: can you scratch it with your thumbnail, easily or only with difficulty with a steel file or if not, does it scratch quartz? Give a Mohs number if you have have the appropriate set of test minerals to determine this . Streak: If you can scratch it, what colour is the powder you get? Is there a distictive texture in massive material . Are there any flat areas which could be crystal faces or cleavage surfaces, and what is the surface of these like - smooth, striated or pitted? Can you see any symmetry in them; i.e. are they parallel but in only one direction like pages in a book ; in 3 planes at approximately 90 degrees forming a cubic pattern, like galena; or 4 directions forming an octahedral pattern like fluorite? What are the features of it's fracture and any fracture surfaces? Is it brittle, flexible, ductile or tough, and is the fracture surface splintery, hackly , conchoidal ? What is it's density: weigh it as accurately as you can, and compare it with similar sized pieces of known minerals; is it's density closest to gypsum, quartz, malachite, barite or cassiterite? .


After you have been doing it for a while and become familiar with the common minerals, you will start to notice some of these features almost subconsciously - like the density of a piece for example; as soon as you pick it up, you will have a feel for whether it's weight is light, about average, or unusually heavy for it's size, and also whether the weight is consistent with other easily observed properties. For example, under my sketch of barite in my mineralogy lab. notebook from A-level geology is the note, "heavy for a light-coloured mineral". This feel is commonly known as the "heft" of a piece -obviously eaiser with moderately large pieces, but it's surprising how small a piece can be "hefted" with a bit of practice.


The Mohs scale of mineral hardness:


1 talc

2 gypsum

3 calcite

4 fluorite

5 apatite

6 orthoclase

7 quartz

8 topaz

9 corundum

10 diamond


Each mineral will scratch any mineral with a lower number, or be scratched by a mineral with a higher number. So if your unknown scratches fluorite but will not scratch apatite, you can give it's Mohs hardness as between 4 and 5. This needs some practice to distinguish true scratching from crumbling of fine aggregates, and to distinguish scratches from a streak of the softer mineral left on the surface of the harder one.


For anyone else to give you helpful ideas for a short list of possibilities, or for you to start trying to identify a mineral from tables in a text book, you will need to observe at least some of these physical properties. A well-focussed photo with accurate colour rendition will also help to shorten the list of possibilities, but a photo alone rarely shows enough diagnostic features for an unequivocal identification, except for well-crystallised examples of common minerals.


An important extra bit of information which I forgot to mention above, is to observe the relationship between the unknown and associated minerals which you can identify. This can often be an important constraint on the likely identity of the unknown, as in a recent post where the unknown was apprently labelled as chromite. In that case, the colour was completely wrong for chromite, but even if it had been dark brown, which would have been OK for chromite, the fact that it was encrusting quartz crystals meant that it could be confidently asserted that it was not chromite, which could be excluded as a possible identity for geochemical and thermodynamic reasons.




Pete Nancarrow


I often refer people to the mineral identification key that Don Peck and I threw together for the now-defunct Bob's Rock Shop website, and which David Von Bargen later upgraded and linked to Mindat from the Mineralogical Society of America website - http://www.minsocam.org/MSA/collectors_corner/id/mineral_id_keyi1.htm That key takes people through the process you outlined in a step-by-step fashion to help them "key out" their mystery mineral. It won't work all the time, but even when it doesn't lead one to a positive identification it at least gives them a bunch of information on their specimen that they can report in a query here at Mindat. This will make it much more likely that the gang can help someone figure out what they have.


My "pet peeve" about the Mindat processes is the terrible photos people post - blurry blobs... - and expect us to be able to ID their samples from them! Even a great photo doesn't guarantee we'll be able to tell what the mineral is - too many look-alikes out there... - so the odds of a terrible shot helping are almost zero. - And the thing is, I see people offering possible IDs based on them! It's "Rorschak (sp?) mineralogy", at best... :~}


KOR!


Alan Plante


Another great help would be knowing the location and environment the piece was found in. I realize that many requests involve pieces without a specific locality, but where known, it would help eliminate many possibilities.


Doug Merson

6th Aug 2008 13:52 UTCDavid Von Bargen Manager

If you want to attach files (photos) to the question please note that they should preferably be in the jpeg format (although gif and png will also work). There is a maximum file size of 1M for the files. You can normally use software that came with your camera to crop and reduce the size of the photo files. 300-400K files can normally give a fairly decent photo of a specimen.

24th Feb 2009 11:38 UTCDavid Von Bargen Manager

For microtests to determine the chemistry of the unknown see http://www.mindat.org/article.php/545/Microchemical+Tests



Sorry to barge in on Dave's message here but I would like to point out to anyone who reads down this far that a very big percentage of the people that come to this forum for help want to try and find out where there specimens come from. All collectors need to glue little locality labels right on to their specimens so that when their normal labels get separated from their specimens, the locality of the specimen will not be lost. If all collectors did this, there would be much less jaw flapping on this forum. Collectors are willing to glue little numbers on their specimens, but not locality names. What kind of craziness is this? As soon as the collector dies and his collection is dispersed which is almost always the case, the little numbers mean nothing. I don't know why I am getting upset about this, because it has almost always been like this and is not likely to change no matter how much I yell and scream.

18th Aug 2010 13:03 UTCGeorges Favreau Manager

May I also suggest that posters be more specific in the title of their post.


For example "unknown #23, please help" may not raise the interest of many people,

but "unknown #23 from xxx mine" is more likely to get reactions from specialists of the xxx mine, if any.


Without writing a one kilometer long title, the more information you can put in the title, the more likely you are to get opinions.

Georges.
 
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