From YPPedia

Leushite
Raw goods
Mass: 4.4 kg	Volume: 1 L
Obtained from: Merchant Brigands, Commodities markets
Used by: Iron mongers, Shipyards,Weaveries
End products: Bludgeons, Cloth, Swords

Leushite is one of eleven minerals. It is an ingredient in swords, bludgeons, and cloth.

German article: Leurit

Spawn Locations

Cobalt	Hunter	Ice	Malachite	Midnight	Sage	Viridian
Conglin Island Cormorant Island	Messier's Crown*	Maelstrom Island*	Akhlys Island Emerald Ocarina* Mirovia Island*	Frond Island The Horseshoe Crabs* Meke Island Oseberg Island*	Jack's Last Gift*	Conglin Island Cormorant Island*

*Islands without market bidding.

Use

Leushite is needed in the production of:

Iron monger products

Rapier (2)

Poniard (2)

Shipyard products

Belaying Pin (1)

Blackjack (6)

Hammer (6)

Weavery products

Maroon cloth (1)

Fine maroon cloth (2)

Real World Counterpart

Y!PP's Leushite appears to be the same as the real world Lueshite, with the same density and color. It is made from the elements Sodium, Niobium, and Oxygen, with the chemical formula NaNbO₃. This is based on the data from http://webmineral.com