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Joe Jenkins
Senior Member
Username: Joe

Post Number: 149
Registered: 07-2006
Posted on Thursday, July 05, 2007 - 12:54 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Purple slates with green spots are usually referred to as "mottled green and purple," or "variegated purple," not Royal Purple, which is supposed to be just purple. However, purple slate can tend to have green in it, depending on the quarry source, and this is not a defect, nor does it undermine the quality or longevity of the slate.
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Terry Hughes
New member
Username: Terry_hughes

Post Number: 1
Registered: 07-2007
Posted on Tuesday, July 03, 2007 - 02:53 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Green (grey) spots are typically seen in red / purple slates and are known as reduction marks. They originated in the mud / silt millions of years before it was was changed into slate (metamorphism). Where there was some organic material in the mud, as it decomposed, it used up the oxygen and this created an electro-chemical gradient. This gradient carried the red pigment (haematite) which gives these slates their colour away from the centre of the spot revealing the underlying green colour of the slate mineral. Sometimes if you look closely you can see a red halo around the spot where the haematite was redeposited. Green marks are not a problem unless they have a soft centre which goes right through the slate. The quarry will reject soft centres so users will only very rarely see them.
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Slate Affair Inc.
Intermediate Member
Username: Slate_man

Post Number: 31
Registered: 01-2007
Posted on Wednesday, March 28, 2007 - 01:43 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Here is a floor I hand picked at the quarry. (Taran Bros) With the same kind of thing happening. This is what give slate a great character. On or of the roof.

slate sample 3
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Cosmo
New member
Username: Ybrw13a

Post Number: 4
Registered: 12-2006
Posted on Wednesday, March 28, 2007 - 10:38 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Thanks for the response. The picture you sent is really wild!!! I would have loved to have that piece on my roof somewhere.
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Slate Affair Inc.
Member
Username: Slate_man

Post Number: 27
Registered: 01-2007
Posted on Wednesday, March 28, 2007 - 06:03 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Hi, there Cosmo I see you are from Rye NY, I did a job a few years ago out by the beach club. But to get to your question. This is common, to have some mixing in colors. A good roofer would try to pull them out as them install them. Here is a picture of a slate that shows how you don't know what mother nature is going to give you.

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Cosmo
New member
Username: Ybrw13a

Post Number: 3
Registered: 12-2006
Posted on Tuesday, March 27, 2007 - 09:57 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

We had just had a new slate roof installed and many of the Royal Purple pieces had large green/gray spots on them. We asked the roofer to remove these pieces and replace them. Does anyone know how or why this occurs. It does not look natural. Have these pieces been dyed?

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