Q. Are Magna Tiles Muktzeh?

A. The translucent magnetic Magna Tiles have magnets built into them on every side and serve as recreational and educational tools that promote creativity, understanding of geometry, symmetry angles, area and perimeter while playing and building geometric figures.

As far as the prohibition of “boine” or building and by extension “muktze”, is concerned they are similar to Lego blocks that many Poiskim permit since they are not intended to bond together and remain attached to each other. The advantage of Lego (and Magna Tiles) is that the blocks can be assembled and dismantled at whim. (Shmiras Shabbos Kehilchoso 16: 18: 53 quoting Horav S.Z. Auerbach zt”l, Yechave Daas 2:55, Tzitz Elezer 13: 30 et. al.)

Horav Shlomo Miller Shlit”a addressed the concern of incurring in the Rabbinical prohibition of “medidah” or measuring (Shulachan Aruch O.H. 323) and the fact that a ruler or measuring tape are “muktze” (Shmiras Shabbos Kehilchoso 29: 43)
However, he compared the use of these educational toys to the use of the Astrolob (a star gazing instrument, possibly a telescope), mentioned in Shulchan Aruch (O.H. 307: 17) that some permit, as Mishna Berura (66) explains; what difference is there if you learn natural science from a book or from an instrument. Although in principle the Magna Tiles are not muktze even for adults, for children that have already reached an age of significant chinuch, the Shabbos hours should be better spent in a more relevant and meaningful spiritual pursuit.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a