Mishnah Berurah — משנה ברורה

Sheep - Or male rams. But all other species such as camels' wool, goats' hair, silk, rabbits' wool, as well as hemp and all similar things... they are not in the category of wool and linen and are not obligated in ציצית except on a Rabbinic level. And [regarding] the wool of an ewe born to a goat, the Beit Yosef wrote that her wool is also not considered wool and is only [considered to be] like the other species. In any case, the same rule applies in regards to all of these [other species]... [that] if he made ציצית [strings out of one of them], it only discharges his obligation if [the garment that he attached it to] was of the same species. [Regarding] sheeps' wool or linen that were mixed with other species... we go according to the majority. If the majority is wool or linen, then it's obligated on a Torah level, and if not, [then it's obligated on] a Rabbinic level. And this is specifically if he mixed and spun [the sheep's wool/linen and other species into threads], and [then] made from them a garment. But if the warp was made from [sheeps'] wool or linen and the weft/woof was made from the other species, or vice versa, then it is only obligated, according to this opinion, on a Rabbinic level... even if the majority was [made] from sheeps' wool or linen... because the warp or weft/woof alone is not considered a garment. And regarding which [species of] ציצית to make for it, see later in Se'if Kattan 13 and see in Biur Halacha.