[DOC] [TLE] Agate Basics [PAR] Although they can form in all types of host rock, most of the world's agates ... 
Other cracks and seams also formed when adjoining sections of lava cooled at 
different rates. ... When the silica concentration became supersaturated, it 
developed a ... Moss Agate Moss agates have clusters of mineral inclusions that 
resemble... [DOC] [TLE] Organic Gemstones: Amber, pearl, jet, dinosaur bone and more! [PAR] Organic gemstones are plant or animal materials that can be fashioned into a 
gemstone. ... materials that have been mineralized (replaced and infilled by 
chalcedony, opal, ... Petrified wood is a fossil that forms when woody material is 
buried, then ... also known as "petrified palm wood," is a material commonly 
found in the... [DOC] [TLE] What is Petrified Wood? How Does it Form? - Geology.com [PAR] Petrified wood forms when plant debris is buried by sediment and then ... It is 
found in volcanic deposits and sedimentary rocks at many of locations ... is 
petrified wood that has been replaced by opal, an amorphous form of silica. ... 
Small pieces of petrified wood can be placed in a rock tumbler to make tumbled 
stones. [DOC] [TLE] Chert: Sedimentary Rock - Pictures, Definition, Formation [PAR] What Is Chert, How Does It Form, and What Is It Used For? ... The name "flint" is 
also used for this material. ... They produce hard parts made of silicon dioxide. ... 
Tons of chert fragments have been found at locations where these objects were 
produced ... has a porous, even texture that makes it useful as a sharpening 
stone. [DOC] [TLE] Chalcedony - Wikipedia [PAR] Chalcedony is a cryptocrystalline form of silica, composed of very fine 
intergrowths of quartz ... The name chalcedony comes from the Latin 
chalcedonius (alternatively ... It is a hapax legomenon (the term for a word found 
nowhere else) so it is hard to ... of different mineral impurities making the stone 
resemble landscapes. [DOC] [TLE] Laterite - Wikipedia [PAR] Laterite is a soil and rock type rich in iron and aluminium, and is commonly 
considered to have ... Laterite ores also were the early major source of nickel. ... 
oxides and sulfates of iron, aluminium and silica under the high temperature ... 
However, if lateritic soils become degraded, a hard crust can form on the surface, 
which... [DOC] [TLE] Rocks and Minerals of Pennsylvania - Pennsylvania Department of ... [PAR] Mar 13, 1994 ... flint, and from hard rocks. Although we ... can also predict what might happen in 
the future. Those clues ... of Pennsylvania called a geologic map. ... Two other 
minerals that are found in many homes are graphite and .... silica (SiO2). ..... 
stone, but other times it breaks down chemically to form a clay mineral. [DOC] [TLE] Visitor Guide - Geological Society of America [PAR] Dec 25, 1972 ... and also catch a glimpse of the GSA headquarters staff at work. .... name the 
street in honor of the Society's benefactor, Richard A.F. ..... for preparation of 
topographic maps. .... silica can be deposited as a filling in the woody structure or 
as a ..... Jasper is a hard, dense form of chalcedony (a variety of quartz). [DOC] [TLE] Contents FOREWORD - State of Michigan [PAR] Frontispiece. Outline geologic map of Michigan........ 2 ... Lake Michigan shore 
near Brevoort Lake. ..... life forms of the Silurian, whereas the middle and upper ... 
In this area also we have the bed of glacial Lake ... Silurian lithographic 
limestone (CaCO3) called the Fiborn ... waste product, (often resembling 
obsidian-volcanic. [DOC] [TLE] Document - USGS Publications Warehouse - U.S. Geological Survey [PAR] Any use of trade, product, or firm names in this publication ... Geologic sketch 
map of Steamboat Springs thermal area, Nev. 14. 4. .... tile elements found in the 
hot-spring deposits at Yellowstone. National .... Silica-saturated water also may 
deposit chalcedony ... stone National Park that is depositing sinter with gold in z. 
0. :::i. [DOC] [TLE] geology and stratigraphy of the central

Question: The name of this hard stone, a form of silica resembling chalcedony, can also be found on maps of Michigan
Answer: flint