PerliteUSGOV.jpg
Description: Perlite (volcanic glass with white powder appearance). Perlite is a volcanic glass that has many industrial applications, because of its light density and insulating properties.
Source: USGSS (dead link; Archived )
Transferred from the English language wikipedia Johan Lont at 11:53, 1 Feb 2005 (UTC). Original upload by w:en:User:Chris 73 .
This image has currency in it to indicate scale.
Using coins for scale is discouraged as it will require people unfamiliar with them to look up the dimensions or guess, both of which defeat the purpose of the object in the first place. Coins can also reinforce a geographical bias, and some coins' designs are copyrighted . Ideally, a photograph should include a ruler with the subject ( example ) or an added scale marking. SI ("metric") units are the most commonly used worldwide (see meter and centimeter ). Images with coins to indicate scale
Common coin diameters for reference:
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This image is a work of the "Minerals in Your World" project, a cooperative effort between the United States Geological Survey and the Mineral Information Institute . The images were featured in the "Minerals and Materials Photo Gallery" on the website of the U.S House Subcommittee on Energy and Natural Resources. As a work of the U.S. federal government , the image is in the public domain in the United States. |