The data types or columns types as they are called are little bit hard to find for somebody who ist not yet really familiar with rails language.
Now here what I found about this:

The columns types are:

:integer
:float
:datetime - default format: ‘2007-07-06 17:05:22′
:date - default format: ‘2007-06-07′
:timestamp
:time
:text
:string
:binary
:boolean

According options are:
:limit, e.g. :limit => 32
:default, e.g. :default => “defaultvalue”
:null, e.g. :null => true means its nullable

and for native data types:
:precision, ??
:scale, ??