The idea that crystals can be considered male or female has it's base in Native American mythology and was origionally touted in relation to Turquoise with the green turquoise being regarded as feminine because of the links to Mother Earth and the Blue Turquoise as being the masculine equivalent - or Father Sky.
Add to this the fact that most practitioners or users of crystals for personal or magical purposes, say they experience a distinct sense of them having a hard (masculine) or soft (feminine) energy when working with crystals.

As with birthstones there was,in the past, a problem with selling "milky" quarts crystals as everybody wanted clear crystals, probably due to most gems being considered more valuable for their clarity. However when the "milky" crystals were re-marketed as being 'feminine/female' quartz, their market value rocketed! The crystals themselves are of no greater or lesser value than before, they were just marketed differently.

Healing with crystals can be dated back in recorded history as far back as Pliny the Elder in AD 70 (it is, in fact, even traceable to Egyptian sources) though in AD 70, Pliny would have referred to any blue crystals as a Sapphire and may have been referring to an actual Sapphire or a piece of Sodalite, a piece of Turquoise or even a piece of Lapis Lazuli as the names of many crystals have changed over the centuries but the main theory behind treatment then was 'treat like with like' showing a link with the Mother Earth/Father Sy principle of the Native Americans.