This tutorial cover the mayor steps from modeling to final image

Basic shapes: create a cylinder with 6 sides, edit them as on the image. Than chamfer the edges twice (no need to use smooth later)
For more complex crystals leave a copy of unchamfered hexagons, also u can use small squares or pyramids

Scattering

Use the built in scatter tool to duplicate the hexagons
distribution object can be a simple plane or for advanced placing a hemisphere (in that case i used a plane)

Scatter settings

Basic scatter settings, fits for all objects i used in the scene
(cilck to enlarge)

Enviroment

its a simple vray studio enviroment, suits for many scenes which requires studio style lighting. Two vray lights, both with around 2-2,5x multiplier


This is how clay looks like in this enviroment, gi settings are all default.

Shaders

So, there are 3 different shaders for the crystals.
A clear, a bit blurry, and non transparent blurry, basically i
only edited them based on some shaders from
http://www.vray-materials.de/ u can download the library:
crystal shaders

Another shader reqiered for compositing (included to library)
thats a gradient whit 100% self illumination, its create the alpha chanell for later composition in photoshop

Also you can use the vray blend material to mix the shaders with the gradient, but i found it extremely slow compared to render the 3 shaders separately. Also composition in photoshop gives more freedome during post process.

Create alpha

This image rendered without gi and background. With the gradient shader. I also made a little less white version for the bottom of the crystals.

 

 

Here are the 3 type of shaders rendered separately and their alpha rendes too. on the next step put them together in photoshop
(i recommend to creat a layer for the background too)

Thats how it looks in photoshop also u can edit the alpha and both the shader layer to make it more exciting, or correct errors.

 

 

 

 

 

 

Final image after some post process