good crystal----high purity and clear
pure and good crystal-----chemical name--SIO2 (silicon dioxide)
-------basically clasify into 1) clear crystal 2) rose ( pink) 3) ametyst (purple) 4) citrine ( yellow) 5) smoky (grey)
-------others: green /blue/ but their base material SI02 are not as high density as above 1)---4)
crystal with different colour because of its different mineral compound such as iron in SI02.

crystal is a natural stone with high frequency and good for meditation (ta Zho) , if u know zi kong , u will know more about it. crystal can expedite and fast initiate your body frequency or more scientific explanation is to make your blood circulation faster becos the related organs have been initiate to vibrate (frequency).
You just sit and calm down and slowly breathing , left hand hold a crystal , you can feel the frequecy flow through your finger to your body.

good Jade----greenish with no dirty substances and internal cracking will be good jade.
upper middle grade--- greenish with little 'dirty'substance but not so obvious , pin holes but filled with wax or other transparent filled/hard material.
middle-----not so green with more 'dirty' substance and filled pin holes. very minor area of internal stone line are 'injected' with green colour.
low------not so so green and internal cracking, many internally area are 'injected' with colour .
rubbish jade---plastic material and 'injected' with colour.

Looking at the packing is hard to distinguish , as long as natural crystal will be good for healing , if you knowing nothing about crystal , prefer clear crystal but be aware artificial clear crystal which is 100% clear , better to get clear crystal with some cloudy stone flow lines internally , natural will be feel more cooler than artificial when u touch it to your face.

glasses can be manufactured into different hardness , drinking glass and car glasses are different grade becos of totally different manufacturing process , where natural crystal is self crystalization under certain temperature/pressure and mineral substance si +o2 in the crystalization enviroment. I remember the harness of crystal or SI02 is 7 but brittle , so it is easy broken if fall to the ground.
I am not expert but interested in crystals and read some its infor.