Is there an issue with wearing a sweater made of cotton and cashmere? Does it need to be checked for Shatnez?
Shatnez only applies to linen mixed with wool from a sheep. Cashmere comes from a goat and is therefore not considered Shatnez when mixed with linen.
Nonetheless, it is recommended that the sweater be checked for Shatnez for it is very common that sheep wool is substituted for cashmere wool due to the prohibitive price, as well as the fact that other threads & fibers are often mixed into garments – although not specified on the label.
.יו”ד סי’ רח”צ ס”א