I'll comment that some of these recent monthly color "themes" seem to be bordering on the very complex to the point of excluding many on the board from participating. I would urge those who plan to be so specific to consider that complex, hard-to-find color concepts may be seen as creative - but they are also very exclusionary. Marbles meeting the above criteria have to meet 3-4 tests.... "snowy mica" not being a minor one by anyone's measure.
I may be misunderstanding the intent of these threads - and perhaps the desire is for them to be small, with limited contributions from board members over the period of a month. As an earlier poster noted - I don't think you are going to get much participation...and when you do it will be contemps (which not everyone collects) and handmades (ditto).
Respectfully,
Alan