hornstone

alternative name sometimes given to chert; also applied by some to other rocks such as hornfels, which is not treated in this document.
Found on http://www.cst.cmich.edu/users/dietr1rv/gemrxAppB.htm

Hornstone

Horn'stone` noun (Min.) A siliceous stone, a variety of quartz, closely resembling flint, but more brittle; -- called also chert .
Found on http://www.encyclo.co.uk/webster/H/62

hornstone

<chemical> A siliceous stone, a variety of quartz, closely resembling flint, but more brittle. ... Synonym: chert. ... Source: Websters Dictionary ... (01 Mar 1998) ...
Found on http://www.mondofacto.com/facts/dictionary?hornstone

Hornstone

• (n.) A siliceous stone, a variety of quartz, closely resembling flint, but more brittle; -- called also chert.
Found on http://thinkexist.com/dictionary/meaning/hornstone/
No exact match found