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About us


I'm Gertie Kostjens.

Professional-Biosensor.com (Part of Crystal Quest, Shop for Crystals and Minerals) is a company that shows my passion since 2002. 

I focus on:

  • Making and selling professional biosensors and energy products.
  • Selling Crystals and Minerals for Energetic / Therapeutic application, but also for collectors.
  • Giving specific advice and individual workshops and courses in those areas where I think I can offer added value.


The passion I feel for the wonderful world of crystals and minerals and the always fascinating field of energetic healing and light work has led to what is now called Crystal Quest. My husband, Jos Kostjens supports me where he can. He also is currently setting up his practice for Coaching, Counselling and Energetic healing, wich is his passion. This practice has the beautiful name Praktijk-Bewuster-leven wich means conscious life and if you want to know more just look at his site

The name Crystal Quest suggests a quest. That is very deliberately chosen. The field of crystals and minerals and Energetic and light work contains so many facets that life just is not enough to know and experience them all.

So I live the adventure every day. I learn, I develop and I express my passion where I can.

Warm Regards, Gertie Kostjens