Gold Sifter

Gold sifters are buildings which use stone to produce gold and later on can also produce sand and very small amounts of iron by puchasing various upgrades.

Creation
Gold sifters are unlocked after buying your first mine. Your first blast furnace costs 100 money, 500 stone, and 200 wood. The cost for subsequent purchases is increased by 1.3x for both money and stone and 1.2 for wood. Also at certain higher levels of prestige you can begin to receive gold sifters for free. This does not affect the base cost.

Production
The base gold sifter generates -20 stone/s + .1 gold/s

With the gold magnet upgrade this is changed to -20 stone/s +.2 gold/s +.05 iron/s

With the destructive sifters upgrade this is changed to -20 stone/s +.2 gold/s +2 sand/s

With both upgrades puchased it will be  -20 stone/s +.4 gold/s +.05 iron/s +2 sand/s

Base
-10(.5/stone)/s + 5(50/gold)/s = -5 prestige/s

Gold magnet
-10(.5/stone)/s + 10(50/gold)/s + .2(4/iron)/s = .2 prestige/s

Destructive sifters
-10(.5/stone)/s + 10(50/gold)/s + 4(2/sand)/s = 4 prestige/s

Both upgrades
-10(.5/stone)/s + 20(50/gold)/s + .2(4/iron)/s + 4(2/sand)/s = 14.2 prestige/s