Hi S! Thank you for your inquiry. Normally two crystals growing together are twins. What you may have is a Cathedral Quartz. This type of Quartz, lets you access the Akashic Records and can bring you in contact with the universal consciousness. I would suggest "googling" images of this type of crystal to confirm that it is the one that you own. A crystal growing on the outside can be a Companion Crystal. This type of crystal can help you with a better understanding of your relationships.
I hope that these recommendations can be of assistance and that crystals grace your journey with love and light.
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Disclaimer – Crystals are not a medical treatment and should not be used as a replacement for medical care. Please consult your healthcare specialist for your particular needs.