The LEGO "Minitalia" was a special serie available only in Italy during the 70s. Bricks are different from the normal Acrylonitrile butadiene styrene (ABS) bricks, but they aren't made of CA (the first material used for molding the bricks): the plastic is a lower quality plastic but it is lighter than the normal ABS and it was possible made trasparent bricks. The most relevant difference between the Minitalia bricks and the traditional ones, is the absence of the name “LEGO” on the top of the studs. 

The brand was born due to many problems with the importing and the selling of LEGO items in Italy during the 70s.
LEGO made 21 different sets. 

LEGO created two series of Minitalia sets. The first one during the beginning of the 70s (and it contains the greates number of sets) and the second at the end of the 70s (probably 1976-1977). This second is a little bit different from the first one because the boxes don't have any "Minitalia" logo and many parts are normal LEGO bricks. Only the windows and the doors come from the old Minitalia serie (in those sets they are black instead the old ones white). The "new" set #1 and #2 were transition sets: note that they, as all the other Minitalia boxes, contain for the first time a 1x4x5 door with four panes and a 1x4x3 window with shutters. Those sets were made of mostly with regular bricks with the addiction of the new types of doors and windows. The first 1x4x5 door, like the 1x3x4 window, was released during the 1977. It’s possible that the Minitalia doors and windows were used as prototypes in those last boxes of 1976-77.

These boxes show that the "minitalia" parts come from original LEGO sets. I think, "minitalia" is mostly unknown because it had few success due to the "bad" bricks. Today it's possible to find them in some old lot of Lego (by eBay or in some flea market in Italy).

"Minitalia was a licensee of LEGO (similar to how Samsonite was here in the US)... their sets are badged both LEGO and Minitalia. Complex parts came from LEGO (for example, boat hulls) but simple rectangular parts and slopes and windows/doors were molded by Minitalia under license. 

ALL of their bricks have hollow technic style studs instead of the LEGO solid studs, but not all have X instead of tubes, some have (sometimes slotted) tubes instead. 
The Minitalia parts are of a different plastic, it's slipperier, somewhat duller and a bit softer. I dunno if it's still a styrene (unlike early Samsonite which is CA) or not. It's not LEGO ABS though, that's for sure. Some Minitalia bricks exhibit mild concave deformation on large flat surfaces, consistent with having cooled quickly and shrank a bit after being molded and ejected.  
I got a MISB Minitalia set once, which I opened, and unless the colors faded while in a non light exposed box, which I can't rule out, the colors are not as vivid as LEGO colors either." 


Minitalia sets:


Picture (Click on the picture to enlarge it): Year:
1 1971
2 1971
3   1971
4 1971
5 1972
11   1972/1974
12   1972/1974
13   1972/1974
14   1972/1974
15   1972/1974
16   1972/1974
17   1972/1974
21   1972
22   1972
23   1972
24   1972
30    1973
31   1973
32   1974
1   1977
These 2 sets, are filled with normal LEGO bricks, and they have no "minitalia" logo. Only the black door and windows are Minitalia parts. These aren't Minitalia sets, these are standard LEGO sets.

Take a look in the old Minitalia schips Catalogue from 1973: