What to Learn?

  1. Structure of the Geosphere.
  2. Earth's crust: types and composition.
  3. Minerals: concept, occurrence and properties.
  4. Rocks: rock cycle, main types and uses.

Basic Information

Rock Grains

Sedimentary rocks can be made up of clasts or detritus (rock grains) weathered from other rocks by river waters, wind, coastal sea waters, glaciers, living beings, etc. This kind of sedimentary rocks are called detrital rocks.

They're classified upon the grains that they are made up of. First up, grains may be all the same size, uniform, as in a sandstone, or different sizes, as in a conglomerate. Secondly, grains may be bigger or smaller. The following table shows roughly how rock grains are classified upon their size:

Diameter
Clay< 0.004 mm
Silt< 0.06 mm
Sand< 2 mm
Gravel< 6 cm
Cobble< 25 cm
Boulders> 25 cm
Mineral Lustre

The term lustre refers to the appearance of a mineral surface in reflected light. The main types of mineral lustre are the following:

LustreOpacityExamples
AdamantineTransparentDiamond
VitreousTranslucentQuartz, Halite, Olivine
WetTranslucentFluorite
ResinousTranslucentYellow and red sphalerite varieties
Wax-likeTranslucentTalc
GreasyVariableMilky quartz
SilkyVariableFibrous gypsum
PearlyPoorly translucentOrthoclase, Mica aggregates
Dull metallicOpaqueCinnabar aggregates
MetallicOpaquePyrite, Chalcopyrite, Magnetite

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About

Science Helpdesk is a website meant to help on developing the scientific contents for the Bilingual Project Integrated Curriculum designed by the Spanish Ministerio de Educación y Ciencia and the British Council.

This website is currently under construction. This means that (a) you could spot some relevant errors in the rendering of the pages - please use the "Contact" form below to report to the webmaster, (b) that it is not feature complete, and (c) and that some sections are a bit short of contents - expect it to be more or less finished by june 2009.

This website has been designed and developed by Arturo J. Murias, currently working in the I.E.S. "Francisco Salinas" (Salamanca, Spain) as a Science teacher in the Bilingual Project.

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