Turning Brown Silica Gravel Into White Silica Powder

[mymachine]

This is the silica gravel that I already own:

http://images-en.busytrade.com/174645700/Silica-Sand.jpg
If I compare to the other silica form such as below silica powder:

silica[/PLAIN] powder
http://lanemt.com/images/golf_sandpile.jpg

How can the brown-color silica gravel tuned into white silica powder?

Thank you

 

[Simon Bridge]

It has to be processed to remove impurities.
There are lots of different kinds of silica and different forms that silicon-dioxide can take.
http://en.wikipedia.org/wiki/Silicon_dioxide

 

[mymachine]

It has to be processed to remove impurities.
There are lots of different kinds of silica and different forms that silicon-dioxide can take.
http://en.wikipedia.org/wiki/Silicon_dioxide

So the brown-color silica gravel and the white silica powder is different?

Or both are the same?

If same, the brown-color silica gravel is being cleaned until the color is white.

Next crush it using the stone crusher machine to get the powder?

 

[Simon Bridge]

If you grind your brown silica it will probably get lighter as it reflects the light differently but basically yes: the white silica in the pic is most likely just a different kind of silica ... probably a totally different manufacturing process.

Your brown silica actually has lots of different colors in it you notice - including plain white. So you could painstakingly go through and separate out the white ones...

"Cleaning" would have to be more than just soaking in bleach or scrubbing with soapy water - it's not "dirty" as such since it is dirt. Some of the actual crystals probably have elements other than silicon and oxygen in it - giving it some extra color - and the grains will be made of different arrangements of the atoms anyway.