Trommel

Improvement Structure Trommel
The Trommel is a unique structure that compliments mining by allowing miners to dump their excess cobble stone into the Trommel to screen it for precious minerals that may have been missed. The Trommel consumes the cobble stone and in return has a small chance of generating Iron, Gold, Diamond, Emeralds and Chromium Ore. The Trommel excretes gravel with a 1:1 ratio as a bioproduct of the screening. Both the gravel and the precious minerals are stored in a single double chest. If the storage chest becomes full the structure will jam and stop working until the storage chest is cleared. It is important that the Trommel's storage chest is emptied often or it will not function.

Besides buying it from other players or the Global Market, the Trommel is the only way to generate Chromium Ore which is an important ingredient in higher tier gear.

How does the Trommel work
The Trommel is very simple to operate, simply select the stack of cobble you wish to deposit it into the input chest. The cobble stone will then start processing and generating gravel and sometimes, if you're lucky, precious minerals.

Screening Chance
The following chances do not take into account the diminishing chance caused by a lower chance item being generated. The trommel randomly picks a number between 1-10000. This number is then checked against the lowest chance item first.

Governmental Effects
As of version 1.757, the trommel is affected differently by government changes due to a refactoring of the code. This change makes Despotism run twice instead of greatly increasing the chances for all items. Inversely, Monarchy and Theocracy now have a 20% failure chance instead of changing the chances for items.

Trommel Upgrades
As of Civcraft 1.6, you can now purchase upgrades to the Trommel. These upgrades allow the trommels in your town to process higher levels of minerals: Granite, Diorite, and Andesite. These higher level minerals have a chance to drop additional items, like Crystals