kazaa81 - 15-3-2005 at 12:35
Hallo to all,
I've bought a mineral, shiny brillant and metallic to apparence.
It is quite heavy (density probably > 5g/cm3).
It is somewhat granular to touch and eyes, abrasive. It is iron-like color, but much brillant, shiny.
I've tried to dissolve a small piece of it in 90% H2SO4 but nothing happened, and the pieces hadn't dissolved.
Can anyone help me to identify this mineral? For example a test to do on it, some minerals which are like my description. I haven't a camera, so
I can't post any photo.
Thanks at all for help! 
Esplosivo - 15-3-2005 at 12:43
Galena maybe? Try reacting a small piece with hot/warm HCl. Being lead sulfide, H2S should be given off (odour) and it should dissolve quite well, the
soln ppting white crystals when cooled due to the low solubility of PbCl2.
Thanks very much...
kazaa81 - 15-3-2005 at 13:07
Hi,
thanks Esplosivo!
It isn't galena (PbS), really!
I've tried what you've post, but doesn't happened anything. I've some galena and it doesn't have any properties similar to
the mineral I'm talking about.
For example PbS is something soft, this mineral is hard, much hard that, when I was trying to get a small piece from it with a 100g hammer, the
hammer's edges became rounded.
Thanks at all for help.
Twospoons - 15-3-2005 at 13:47
Haematite? Try abrading with very fine wet sandpaper (like 1000 grit). Haematite with give a dark blood red colour to the wet paper.
12AX7 - 15-3-2005 at 15:20
Hmm, ain't silicon (polycrystalline), carbon of any sort, a carbide perhaps? Man-made? Possibly a ferroalloy (ferrosilicon, ferrochromium,
etc.)?
Tim
Saerynide - 16-3-2005 at 05:15
I was about to suggest silicon as well. If its very shiny, with a bluish silver tinge, it very well could be Si. Si lumps are quite dense and hard.
chemoleo - 16-3-2005 at 05:27
How about a Bismuth crystal? There's a thread on it, this should help with you the analysis.
Also I suggest a density measurement - weigh the piece, and then drop it into a graded measuring cylinder, and see how much volume it displaces, and
calculate the density from it.
Bi has a high density.
neutrino - 16-3-2005 at 14:03
Nope, bismuth is very soft and weak. You can easily break plates a couple of mm thick with your hands.
chemoleo - 16-3-2005 at 15:27
Sure. The crystals are hard though. The surface is hard too. The Bi I got is a big fat bar that is certainly not bendable easily. Anyway..
Kazaa, try and melt a little bit under the flame. What happens?
neutrino - 16-3-2005 at 16:33
Both my ingots and the crystals I grew are rather soft; I can dent the stuff with my fingernail. This doesn’t exactly match up with the damaged
hammer thing. The difference is that my bismuth is 99.99% pure, while his would be much lower due to being a raw mineral. Would the impurities
strengthen the metal that much?
Density of mineral....
kazaa81 - 19-3-2005 at 13:51
Hallo to all,
I've measured the density of my mineral by placing it in a graduated box with water, weighted, and measured the volume occuped.
The density has resulted something 3,7-4,0 g per cm^3.
Hope that this help. Thanks at all!
Saerynide - 20-3-2005 at 00:54
I havent been able to find the density of crystalline Si, so I dunno whether the density matches.
Heres some pics of Si crystals:
or
12AX7 - 20-3-2005 at 11:28
AFAIK, silicon is close to aluminum, just a little over (SG = 3 or so). It's a little darker than most shiny metals and definetly glassy, though
that may be missed on polycrystalline samples (most Si you'll find was probably a chunk (hence either polished, or conchoidal fracture) of a
99.9999% boule).
3.7 to 4 sounds a bit heavy. Do you have a picture? Mohs hardness test? Streak test?
Tim
To Kazaa
Minus459F - 29-3-2005 at 10:05
I'm not sure, but I suspect what you have is an iron concretion. I picked up some several years ago and marveled at the weight of them. Very
hard. I happen to know a minerologist and took the sample to him. Nothing special, just something that happens in water sometimes. If you can find
enough of it you can sell it as iron ore.
To see if you have the same thing I had, use a grinder and try to grind away a portion of it (this is not really easy to do). The ground surface will
be shiny, as if you had ground away iron, but it will not look exactly (but close) like iron in color and reflectivity because of the silicates in the
matrix.