Book 1, chapter 8 "Old Cave" HELP

I have mined all silver spots but am lacking 10 coins to finish the chapter. Can someone please give me a hint? I've been searching forever! Thanks!

You can find silver in some of the hidden caches.

But the best way to gain more silver is to pick Rock until you can build the stairs to where the cave is. Do not pick any silver.
Build the Storehouse as soon as you are able.

Now you can start mining for silver.

The Storehouse building gives you +10 resource for everything you get; food, wood, silver.
This means that when you mine for 10 silver, you automatically get 10 extra if the Storehouse is built.
Same with food, wood and stone, bombs, and whatever you find in the secret caches.
A very useful building!

Example: The silver deposits near your camp give you 50 silver when you mine them, you can "pick" them 5 times before they run out.
But if you have the Storehouse, you get 100 silver instead of just 50.

Thank you!!