Borehole troubles

[fender]

I have had five or six games using an ICS type setup and in a few of them, early in the game, boreholes were only giving 2 minerals. They did change to give 6 minerals, but I didn't notice anything that I had done or discovered that caused this.
I reinstalled the game and the first try was normal, 6 minerals. The second game however went back to the 2 again, and then again for no reason that I know of, returned to 6.

This may be normal, as I didn't use boreholes and crawlers quite so soon in the game before. My question is, what is going on here. Is this normal? And what causes the change from 2 to 6, or better yet, why do the boreholes sometimes only give 2 minerals in the early game?

I can't be sure for all the games, but I think I had the WP in the ones that did this.
Thanks.

[Illuminatus]

Boreholes give only 2 minerals (unless built on bonus minerals which negates teh penalty) until you discover EcoEngineering, like other terraforming (capped to two without bonuses unless on bonus until appropriate technologies discovered). It is prefectly normal.

[fender]

Thanks, that clears things up.

[Chaunk]

You normally can't build boreholes without the WP before Ecological Engineering, which may explain why you haven't noticed that before. FYI.