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 [see below]. Streak: If you can scratch it, what colour is the powder you get? Is there a distictive texture in massive material [granular, platy, fibrous etc]. 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 [e.g. mica]; 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 [like a piece of cast iron], conchoidal [like broken glass]? 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? [or if you have none of those, use non-minerals; compare it to a piece of pine wood, aluminium, iron or lead].
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 - [
www.minsocam.org] 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
