The pick-ax is a tool used by Twinsen in a couple of occations in Zeelich. It is bought in a bazaar in the Island of the Francos for 20 zlitos. It can be used to dig in the grass part where the fragment of the Francos is buried, and in a rock crystal in the Island of the Celebration to get a piece of rock crystal, needed to get the pisto-laser working.
"This pick-ax will allow you to dig into the ground or harder materials. With it, you can now locate objects buried underground, or extract materials."