Rock butter

Rock butter (also known as stone butter) is a soft mineral substance found oozing from alum slates.

Rock butter

It consists of native alum mixed with clay and oxide of iron, usually in soft masses of a yellowish white colour, occurring in cavities and fissures in argillaceous slate.

References

• http://dict.die.net/rock%20butter/—has information from Webster's Revised Unabridged Dictionary (1913)
• Rock Butter, from the U.S. Bureau of Mines' Dictionary of Mining, Mineral, and Related Terms (1996), online at the Hacettepe University Department of Mining Engineering website.
• This article incorporates text from a publication now in the public domain: Wood, James, ed. (1907). The Nuttall Encyclopædia. London and New York: Frederick Warne. {{cite encyclopedia}}: Missing or empty |title= (help)
• This article incorporates text from this source, which is in the public domain. Porter, Noah, ed. (1913). Webster's Dictionary. Springfield, Massachusetts: C. & G. Merriam Co. {{cite encyclopedia}}: Missing or empty |title= (help)