Deva, Shoten Zenjin , Angels, Fairies , Nature Spirits , Gods (Major and Minor), these are some of many names for the/those consciousness  who are the guides, guardians, conscious mind and spirit , messengers, beings   who oversee and implement the Cosmic/Divine order /plan . The concept of  Nature- Spirit  is that everything  is alive and has consciousness. Everything is one entity and all beings , things, feelings, experiences, are aspects or parts of that One  Unified Isness.  Those apparent  parts are also each individual consciousness and beings whether of physical, emotional, mental or spiritual substance .

One Definition or explanation of Deva is as protective forces of the universe, as builders  of the movement of life energy from Spirit and energy  into Form and Physical and of the return or pulsing of the form into spirit.
 You may find the term Angel and Deva to be used somewhat interchangeably.
Others interpret Angels as being non Physical beings who oversee the evolution and communication of Humankind and their relationship with the Divine or Unified Essence (God/dess) and Deva as being non Physical beings which oversee the evolution and communication of all other  entities (including crystals as well as plants ,animals , Elements, weather systems etc.) with the Divine and with humankind and all other beings. When you accept everything as being facets of One Entirety of consciousness, the distinction between Angel and Deva may be somewhat  arbitrary.

Crystal Deva are Nature spirits of the order of all that is or can manifest as  crystal ,stone or mineral.  The overseers of the aspect of the cosmic plan/order as it relates to crystals etc..
Crystal Deva are the consciousness of  the crystals, the spirits , the minds and souls of the stones .They are individual spiritual, mental, and emotional aspects of each crystal or stone. They are the collective mind of each kind of  stone. Crystal Deva are the over lighting essence and unified consciousness of all crystals and stones and all that pertains or relates to stones  . Crystal Deva are/is a manifestation of the undifferentiated creative source  law, rhythm, power, of the universe . They are aware, conscious, energy of  the crystals manifesting in a way that enables us to better communicate or  understand or at least conceive of what it is they are and how to work with them and the physical form of the rocks crystals and minerals. Crystal deva, crystals and stone are also associated with the planet Saturn and Saturn energies. The Saturn Angel, Deva or Logos is considered by many to also  be the overlighting intelligence as related to Stones. 

I experience the Crystal and Rock Deva as being the spirit of the crystals, the soul and intelligence.   You may sense communication with them them as energy, receive words or images, colors, music or just an intuitive knowing. You may not consciously sense the deva yet may still be interacting with them. Sudden insights are often the result of assistance from deva. Meditation and observation on and with nature including the stones and  crystals that you encounter  are gateways to awaking this communion and communication.
It is possible to experience the Deva as  mind/spirit essence providing an overview of the spirit of Stone. During this  you may feel an embrace of energy  which may or may not be accompanied by messages perceived in words or visions and colors and physical and emotional sensations. Sometimes this has been a very dramatic experience but more often it is quite subtle and manifests in the background.

The traditional interpretation of the Devic beings or intelligence's of  nonphysical  planes has been expressed in a very hierarchical way. A  contemporary  understanding is that such hierarchy is  more a matter of an ordering for our limited understanding in body than a true matter of  absolute rank because each Devic aspect or entity may at any time be merged with the whole and  can also be presenting as an individual or group of conscious entities.
So that there may be Deva of  all plants, Deva of specific plants, such as a Strawberry plant Deva  but you may also encounter a Strawberry leaf Deva, a  Strawberry flower deva and a Strawberry fruit deva or even a Strawberry root deva . These may  be seen as the aspect that provides the template for the physical form of each part but may also give you specific information about the meanings and purposes  of the part of the plant or the whole plant or of plants of that kind. Everything , every aspect of everything, even thought  and emotions can be said to have Deva or awareness.
Some people see or sense  Deva  in a mental image or even in the outside environment .
The form seen is usually taken from the mind of the viewer and the collective mind/record  to assist in the communication. The nearest to an actual form of most deva would probably the glowing orbs or ribbons of light that are sometimes sensed .

Going into meditation and communing with individual crystals and with crystal Deva is a way of receiving energy and information pertaining to life and the crystals. Crystal Deva often carry and convey ancient records and wisdom via the crystals. The Deva can really help with your healing and spiritual evolution and you can help them in the harmonizing and achievement of the highest evolution of manifest reality.
People  have recently (the last couple of thousand years or so ) not been very receptive to accepting to or appreciative of the Deva.  This has not had as much  adverse effect in most cases  with the relationship of the stone people and humankind to the extent that it has with some other Deva. Though some people  might still pick up sadness , pain or  even anger  from the Deva and stones  of areas where the land has been disturbed  by reckless blasting or other human actions with negative impact. The Stones also sometime reflect back the emotions  of the person or people around them or of events that they have recorded in some way.
When you approach Deva and  are  open to receive contact with a respectful and appreciative heart and mind then such transient sensations if any usually are brief before a deeper communion and communication is begun.
This communication may be quite subtle  at first (not always) do not be disappointed if you do not have the kind of immediate connection you might get when you strike up a conversation  with an old acquaintance.

Be open to contact , Be open not only in meditation but as you walk in nature, as you hold and gaze on the crystals throughout each moment of life  because communication can occur at any time. You may meet Deva in your dreams  or under the most ordinary of circumstances.
Ask what you may do for the Deva but do not promise to do something that you cannot do.  Tell the Deva what you wish to know, pay attention to all information and sensation that occurs. Thank the Deva for the contact.  You may wish to make a symbolic gift or an offering of thanks and respect to the Deva. Some people make offer  a scattering of corn meal or tobacco,  if this is a traditions you follow. When you have returned to normal consciousness you may want to ground yourself and   you might wish to make notes to record your memories and impression while they are fresh.  Some people even learn to make notes or to speak into a tape recorder during communication.
As long as you continue to be open to messages from beneficial non physical beings you will be strengthening  your ability to connect with energy and information from the Deva.
As with angels and Other Spirit guides You will probably at first wonder if the contact is only your imagination and doubt that it is real. Then you will begin to realize the quality and validity  of the  information Then you may begin to  sense the various Deva that awareness may become more  concrete  and you may even become aware of a feeling of   union with the Deva and all live and the divine however you perceive it  and you will come to have trust and confidence in the communication and know that you are never alone.