It is impossible to say just from the BSE image you provide. Some EDS/microprobe data would be very helpful. It looks like a hexagonal crystal. Moreover, the BSE value looks quite low compared to the molybdenite, suggesting it is a more complex (silicate?) mineral with a substantial proportion of lighter elements. Try the search-by-chemical-composition search onmindat.org. Between it being a hexagonal mineral, molybdenum-bearing and containing a large proportion of lighter elements there are not many options left.

http://en.wikipedia.org/wiki/Category:Molybdenum_minerals

What is the elemental make-up of this 'new' molybdenum mineral? I presume that it is a sulphide since you mentioned floatability. A little more detail would be very useful.

There a few molybdenum minerals that do not float or float well at all - mainly so-called 'oxide' minerals.

I have encountered molybdenite that does not float well - apparently due to some oxidation (geological) effects (no mineralogical research was done). Previous research, as well as literature, shows that it is very hard to depress molybdenite using very strong oxidants so we were a little surprised. We managed to significantly improve floatability by employing xanthate esters and the like.

Perhaps a different collector would improve floatability of your molybdenum mineral.

We once have found molybdenum in some areas in some unusual silicate phases. I wouldn't rule out oxides yet from the information you have provided. What float parameters are you using? Which collector and are you sulphidizing with something like NaHS? Just because it is reporting to tails, it does not necessarily mean that it does not float. You need to look at the operational aspects of your float cells as well.

In our experience the major distinguishing factors affecting MoS2 flotation are traceable back to morphology and pulp chemistry effects. Poorly floating MoS2 can be very fine (flake nature makes particles move around bubbles with the streamlines and negatively-charged and reactive edges offset basal plane hydrophobicity), or MoS2 of all sizes can be bent, exfoliated, etc. (resulting in more edge to face exposure ratio and the jamming of hydrophilic gangue such as clays in between the "leaves") or, the presence of divalent cations in process water can adsorb to edges and bridge to fine silicates. All te above make the job of oily collectors more difficult. At very fine sizes, any compositional analysis technique such as SEM/EDX etc give spurious results due to the mismatch between image and analysis resolution. EDX will give you, at best, 5 micron analysis volume (in depth as well as laterally) so you will not be analysing the particle only.

See:- Zanin, M., Ametov, I., Grano, S., Lin, Z. & Skinner, W., A study of mechanisms affecting molybdenite recovery in a bulk copper/molybdenum flotation circuit, International Journal of Mineral Processing, 93(3-4),256-266 (2009)

and the PhD Thesis of Lin Zhou (University of South Australia)

In 20+ years, I am yet to see convincing evidence of MoS2 compositional variation unless it is a trace substitution of an impurity or confused with attached material.

We have found some evidence of silicate phase in this minerals while exact composition is not clear for us. Further study is going on. From floatability I mean RECOVERY. As new mineral of molybdenum observed in the feed, a decrease in recovery would happened. This stage in bulk flotation of copper-molybdenum and usual reagents are utilized.

According to Paul Ramdohr (1980, The Ore Minerals and Their Intergrowths, Page 878)

Jordisite is MoS2 amorphous to X-Rays, which occurs in semi metallic masses of anthracitic aspect in low temperature deposits; e.g. Bleiberg in Carinthia, and forms there the base for the development of wulfenite. There are many indications, that medium – temperature (also in collection) to the ink blue ilsemannite. One sample of Jordisite from Mesiza in the Karawanken shows all transitions from complete isotropism to strong unisotropic masses.

* we say this mineral is Jordisite? Further information is appreciated.

Do you know a solution to improve recovery of (Leafy Molybdenite, Above Fig, Upright)?

When you say the usual reagents for Cu-Mo recovery, could you be more specific about which reagents and operating conditions are being used?

I am a late entrant to this discussion. As per SME Mineral Processing Handbook there are 12-14 minerals of Moly but the main is molybdenite. Molybdenite is naturally floating and there should not be any problem in recovery. In copper moly bulk floatation circuit more than 80% of the moly reports with copper concentrate. But in many ores there are graphitic/carbonaceous material which causes enormous problem in achieving desired product moly grade. Colour wise they both look similar. So where are you losing the moly, in the bulk floatation stage or in the moly recovery circuit?

https://www.911metallurgist.com/blog/molybdenum-ore-processing-moly-flotation