I would guess it has to do with moisture-spent some years climbing on sandstone out west.
Moisture caused some types of discoloring but if I remember most discolorations were black and similar to what's on your stone.
Maybe it is lichen growth-interior or exterior?
Maybe you need a mildecide , fungicide, biocide product.
On Mon, Mar 30, 2015 at 9:46 PM, <hectorcastillo@comcast.net> wrote:
is the black in the grout ?Hector CastilloFrom: "Hector Castillo" <hectorcastillo@comcast.net>
To: sccpartners@stoneandtilepros.simplelists.com
Sent: Monday, March 30, 2015 5:21:36 PM
Subject: Re: Trying to figure out what this isTry solvent for a testSent from my Verizon Wireless 4G LTE smartphone-------- Original message --------
From: Mike Marsoun <nulifesc@bigpond.com>
Date:03/30/2015 5:02 PM (GMT-08:00)
To: sccpartners@stoneandtilepros.simplelists.com
Subject: Re: Trying to figure out what this isIs that sandstone? I see that a lot. Nothing will take it out. I have tried pure bleach sitting overnight. Nada.Sent from my iPhonePeroxide did nothing, It's chiseled sand stone and these spots are on random tiles here and there with no connectoin to plants etc. any thoughts?
Thanks
stephen
-------- Forwarded Message --------
Subject: What? Date: Mon, 30 Mar 2015 10:57:07 -1000 From: Stephen <mauiwebbs@gmail.com> To: stephen@newlifemarblerestoration.com
This email is free from viruses and malware because avast! Antivirus protection is active.
Visit list archives, subscribe, unsubscribe or change your subscription preferences: http://stoneandtilepros.simplelists.com/sccpartners Start a new conversation (thread): sccpartners@stoneandtilepros.simplelists.com<IMG_0212.JPG>Visit list archives, subscribe, unsubscribe or change your subscription preferences: http://stoneandtilepros.simplelists.com/sccpartners Start a new conversation (thread): sccpartners@stoneandtilepros.simplelists.comVisit list archives, subscribe, unsubscribe or change your subscription preferences: http://stoneandtilepros.simplelists.com/sccpartners Start a new conversation (thread): sccpartners@stoneandtilepros.simplelists.comVisit list archives, subscribe, unsubscribe or change your subscription preferences: http://stoneandtilepros.simplelists.com/sccpartners Start a new conversation (thread): sccpartners@stoneandtilepros.simplelists.com
--
Regards,
Stu Rosen
201-446-1200
Stu Rosen
201-446-1200
"EVERYTHING MATTERS"