Disclosure, and what silence implies
Updated
A important commercial habit in this trade, and the one that compounds.
The rule
Anything a knowledgeable buyer would want to know goes in the description.
Not "anything you are asked". The buyer cannot ask about what they do not suspect, and the dealer is the one who knows.
What has to be said
Damage. Every break, chip and bruise, and where. Contacts are natural and worth distinguishing.
Repair and restoration. Rejoining, filling, reconstruction, and composites absolutely.
Treatment. Heating, irradiation, dyeing, coating.
Uncertainty in the locality. "As received" and "unverified" are the right words.
Uncertainty in the identification, and its basis.
Instability. Whether it is a fugitive color, a dehydrator or a sulfide that may decay. This one is rarely disclosed and it is the one that most affects what the buyer is getting.
Why silence is read as a claim
Because the trade convention is that material is as found unless stated otherwise.
So an undescribed repair is not an omission; it is an implied assertion that there is none. That is how a buyer will see it and how a dispute will be judged.
And it will be found. Buyers examine under magnification and under UV, and repairs and coatings show.
How to say it
Plainly, in the description, not in a note somewhere.
Photograph the damage as well as the good side. A listing that shows the flaw sells better than one that hides it, because it makes the rest of the description credible.
And put it on the label too, so it travels with the specimen after you.
The economics are simple: a small number of people buy and sell specimens repeatedly over decades, and reputation in that group is the whole business.