Misshipped Marble

[Brett Campbell]

Good Afternoon,

Thanks to all for al of your time in helping others. The time and frustration you have saved others is invaluable. I hope once I become more experienced with my equipment I may be able to help others with their problems. As a new Engraver I have a lot to learn and many questions. However, my question is one that can only be answered by the experience of others.

Has anyone recieved black granite in place of black marble? This has happened to me twice with only three orders. Laserbits and laser sketch, were whom I ordered from. I tested these tiles with vinegar, a previous post said that marble will react with acid, and it resulted in the majority of my tiles are granite not marble. Am I extremely unlucky or is this more than coincidence?

Thank You,

Brett

[Joe Pelonio]

It sounds like you are unlucky. I have so far been able to buy marble and granite locally, so I can pick my own out, and don't have to pay shipping. Granite is great for laser work too, but a lot better for clipart and text than photos, compared to marble. It seems like you can also tell by looking at the edges and backs. Sometimes larger tile stores sell marble. If not, there are usually custom tile and granite places that will order it for you, or sell you leftovers from kitchen counter jobs. Of course not many people get solid black for their kitchen.

Here's a couple that I've used here, maybe there's a similar place near you?

http://www.stonewoodonline.com/

http://www.northwestmarble.com/

[Bill Cunningham]

Marble is a fairly soft stone, you can gouge the back of a tile with the point of a knife.. Granite is very hard, much harder than marble.. Marble goes almost pure white when hit with the laser beam, granite goes to the same colour as the back of the tile..Usually a shade of gray..

[Roger Jones]

I was a mining company geologist for 25 years. One of the problems here is that names applied to building stones are not necessarily correct using geological nomenclature. Geology texts will tell you that marble effervesces in vinegar, however if the marble is high magnesian (dolomitic) or high iron (ankeritic) it will not effervesce in vinegar but will effervesce in warm hydrochloric. The darker the marble the more likely it is that it is not a (geologically) true marble.

By the same token, to a geologist, granite is never black.

The upthread comment about hardness is generally true but the blacker the "granite" the softer it will be. It will, nevertheless, be harder than any marble. A true white or pink granite will not, or barely, be scratched by a file whereas the darker forms will be scratched fairly easily. The same file used with the same pressure will leave a deep gouge in marble.

Roger

Brisbane, Australia