Crystals can be found in any asteroid belt in the game.

Fly into an asteroid belt and stop your ship. Focus your camera so you can see alot of roids on screen stop your ship and wait for a few seconds. You will see that some of them blink every few seconds if youre close enough. These blinks are the reflections of Crystals growing on the rocks.
If you fly closer to a "ping" youll notice a small targetable crystal on the rocks surface which you can shoot with any shipweapon. The crystal will burst into shards which can be collected either by flying through them or using your tractor beam to collect them by holding the "O" button (default key).

The crystals have different colours and can be extremely valuable and collecting those is probably the fastest way to earn money as a beginner!

There are 5 types of crystals:

Purple : Bandannite - Very common - Price 1k cr
Blue : Menelaene - Common - Price 10k cr
Yellow : Aguilite - Rare 20k cr
Orange : Mitonene - Very Rare 30k cr
White : Burnite - Super Rare 250k cr

-All prices are average and will change randomly at stations.
-All crystals are inventory items and cannot be remotely collected.
-Crystals can be sold at station traders.

Frequency:

Legend:
Im using signs to describe the cystal" ping" frequency.
Imagine a morse code for easyer understanding.

(-) = single ping followed by a long pause
(*) = fast ping (usually followed by a second fast or very fast ping)
(.) = very fast ping (usually followed by a Fast or very fast ping)

Every crystal has a blink frequency (i called em ping) :

Purple : Bandannite: - - . .
Blue : Menelaene: * * . .
Yellow : Aguilite: - - * * *
Orange : Mitonene: - - - * . .
White : Burnite: - * *

When Watching an Asteroid field and focus on single "pings" you can determine the valuable Crystals by their ping-frequency and save alot of time by only collecting the most valuable ones.
This works in theory but there are a few difficultys ill explain in the last guide chapter.

There are two problems with cystal identification that make it hard to use this info properly to get only the most valuable crystals:

First:
All of the asteroids rotate with different speed! So you may be unable to see the full cycle of pings because the roid has moved and the crystal has moved to its non visible side.

Second:
The Ping frequency of the most valuable crystals are very similar to the frequencys of the cheapest ones! To Confirm the frequency you have to watch for multiple cycles and even then there is a good chance you will find a purple one instead of a white crystal. Spotting whites requires some experience and even i still have a success rate of aproximately 33% spotting the right crystal.

Tipps: Despite the two difficulties , how can i save time and still make money quick?

-Activate the scanning mode by pressing shift+2 for easy spotting.

- Go for Tripples! If you see a tripple ping go for it! Its either a yellow or orange crystal and those are quite easy to spot and spawn in decent numbers = easy cash.

-i think the more dangerous sectors have a higher density of high value crystals. I checked it and it may be true but ive also had good finds in the central sectors as well.
A good place to mine is the sector Faulty Logic I after you breached through the entrance there are belts with high desity in the north western part of the system.


- There is another trick but may be seen as an exploit of a game mechanic or at least in the "grey" area !

Stop reading here if you want to work hard and honest

You can move a ship into the center of an asteroid belt and park it there. then teleport to another sector and then back into your ship. you will notice that all pings are now alligned. All pings start at the same time so ull see all of them blink at once. this makes it easy to identify the very common purple crystals and then you just have to lookout for those crystals that dont match the alligned pattern. Give it a try youll see what im trying to show you :) .

Have Fun with this guide and any feedback is welcome.

Im not a native english speaker so take it easy if you find any spelling mistakes.