Obsidian. This block is difficult and dangerous to obtain, often found amid its constituents: water and lava. Once acquired, it is used in some high-level crafting recipes that can vault the player to the next level of the game.
This cache has no preliminary requirements. It is a traditional hide on Lock Island in the middle of the Potomac River. Parking coordinates are for Riverbend Regional Park, where boat rentals are available on Fri-Sun in season (May-Oct) and when river levels are not too high. Here is a web site with more information. The paddle is upstream and will take some effort to get there. Once on the island, there is a minor tree climb to the tethered lock-n-lock (hey it is Lock Island after all!) Please use caution when attempting this cache.
Current Potomac River Conditions

Congratulations to T_N_C for making their 100th cache find here!

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Links to caches (click on rectangles in image). Arrows show which caches are prerequisite to find other caches in the series.
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