Minerals are the category where parcels are heaviest for their size, and where the weight most often surprises the seller.
What decides it
Weight, and then the points. A small specimen can be surprisingly dense, and a box of them is a serious parcel. Use a weight rule and weigh the packed box, not the stone. How delivery is charged.
Then the fragility: terminations chip, and a chipped point is most of the value gone. Double-box anything fine or bladed. Packing minerals.
The four options
Courier for most specimens, well padded. Your own delivery locally, which works well for larger pieces. Pickup for big geodes, heavy display pieces and bulk lots. Buyer arranges for the largest.
When collection is the honest answer
For anything large or very heavy, where the delivery cost would approach the value of the piece. Say so in the listing — pickup terms are agreed before bidding, with a collect-by window of 72 hours unless you set otherwise. How pickup works.
Combining wins
Combining works well for small specimens and badly for heavy ones. It is on by default and you set what each later win adds; in this category that figure should reflect weight rather than count.
One thing to check first
Some material in this category cannot be sold at all — coral, ivory and the shells of protected species are wildlife products, and much of what people call a fossil can fall under antiquities rules. Settle that before you worry about the parcel. Prohibited items.
Questions people ask
Should I use a flat rate?
Only with a weight rule behind it. Density varies enormously here.
Is a padded envelope ever enough?
For a small tumbled stone, perhaps. For anything crystalline, no.
What about very large geodes?
Collection, said before bidding starts.
More: setting up delivery, selling minerals.