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[jorge santos garcia]

Hello all

I have a biterminated quartz crystal, with one terminated point at one end and two terminated points at the other end. It seems to be one crystal, see anything that can make me think of two crystals growing side by side and their surface is at the same plane, only a 1mm difference near the top of the two terminations.

II want to know if this is a twin?

Join 2 photos of the crystal.

Thanks for your help

Jorge

[Gerhard Niklasch]

Hi Jorge,

I would call this an example of parallel growth, but not of twinning.
Twinning by definition adds a (plane or axis or center of) symmetry which an untwinned crystal of the same mineral does not possess - which is not the case here.

There was a thread about this on mindat about a year ago, where you'll find a couple of further references worth looking at:
http://www.mindat.org/mesg-62-140655.html

Enjoy,
Gerhard

[Jordi Fabre]

I agree, isn't a twin but a parallel growth, typical for the Panasqueira's Quartz.

[John S. White]

In fact, it appears that it started out as a single crystal and experienced interrupted growth, causing the crystal to split into two parallel crystals.

[jorge santos garcia]

Thank you both. That's what I thought, but was not certain.

Jorge