ET / Extra-Terrestrial / Extra-Termination quartz crystal has a single termination at the top and the base has several terminations. I tend to call them ET or Extra-Terrestrial over Extra-Termination.

Because of the way the base looks, Extra Terrestrial crystals remind me of a rocket ship (imagine the flames coming out of the bottom of a rocket). 

Extraterrestrial crystals have a powerful energy. You may use them to assist you in accessing beings from other realities (extraterrestrials) and Angels.

I often experience a feeling of travelling in space when I hold them (I get a visual of being in space, with stars whizzing by).