Which one? There isn't just one. Genetic sex chromosome mosiacism almost always presents with male sex organs in the presence of a normal Y chromosome or even X chromosome with SRY gene expression, such as the case of XXXXY, XXXY, XXY, and male XX. If there is abnormal or absent SRY gene expression in Y chromosome replication, such as female 46XY, they will exhibit female sex organ characteristics. SRY is responsible for the production of testis determining factor which causes the formation of testes and thus testosterone production which leads to a male fetus. Some other examples of genetic mosaicism include congenital adrenal hyperplasia (CAH) 46XX females who will develop outwardly pseudo-male appearing genitalia unless treated with corticosteroids, but they actually have a uterus and other normal female parts.
If you're referring to 45X/46XY mosiacism, that's the one that is most likely to present with what you're referring to as intersex (it's scientifically called genital ambiguity), although most 45X/46XY present as male in regards to external genitalia. External and internal masculization scoring do a pretty good job at detecting which are "males" and which are "females," even though the parents may not rear based on the presentation. Males with micropenis are more likely to be raised as females and some females with an obvious vagina and uterus are raised as males. The majority of long term studied 45X/46XY males reach male puberty without any hormonal supplementation. It all depends on where the 45X cells are formed. If the majority of sex organ cells are formed by 45X cells, which is uncommon, they will generally present with external female genitalia (may have clitoromegaly), some form of a vagina and uterus, and will almost always have streak gonads that can present as some form of testes or ovaries, or one of each. The females often require hormonal supplementation as the streak gonads aren't usually functional due to the presence of only one X chromosome. 45X/46XY individuals are fairly rare.
If you're referring to 46XX/46XY, that isn't genetic mosaicism. That's a chimeric genetic disorder. They can present with genital ambiguity, true hermaphroditism, or normal genitalia dependent on where the XX and XY cells are located. Again, these are pretty rare, at least in case study.
Just for the humor of it, here's a satirical scale for determining sex in genital ambiguity.
