Final answer:
The velvet sack was found filled with gold dust, an assertion supported by various textual examples where characters discover and value gold in unrefined forms. The process and reactions depicted emphasize the precious and sought-after nature of gold.
Step-by-step explanation:
The contents of the velvet sack you found filled with are indeed gold dust. The excerpts provided consistently illustrate instances where characters encounter gold in various forms, mostly in unrefined states such as dust or nuggets. The act of packing the earth into a box at a table suggests preparation for gold panning or similar activities, which was a common method used to search for gold in streams or rivers during historical gold rushes.
Descriptive phrases such as 'washed it out of the stream' and 'picked it out grain by grain, nugget by nugget' convey the meticulous process involved in collecting gold dust. Further discussion of the gold's value, evident through expressions of shock and notions of wealth, reinforces the significance of this discovery. Finally, characters actively seeking confirmation of the substance's authenticity, such as by 'feeling if the gold was real' or being mesmerized by the sight of gold fillings, further underlines the precious nature of the material in question.