What is a mineral? A mineral is (generally) an inorganic, naturally occurring, organized crystalline structure composed of a single chemical compound or element.
What is a rock? A rock is (generally) a natural solid composed of multiple crystals of one or more minerals. Although many rocks contain visible crystals of individual minerals, a rock itself does not have an overall crystalline structure.
What is a crystal? A crystal is an orderly arrangement of molecules formed because the component atoms and ions tend to aggregate together in certain specific patterns. Sometimes very different minerals are formed from the same starting materials (such as diamond versus graphite, both pure carbon) as determined by the temperature, pressure, or other conditions of formation. These arrangements result in the crystal forms described in the physical characteristics pages. Often, minerals are formed as a solution changes in some way which allows or forces the component mineral(s) to solidify or precipitate out of solution. This change may be temperature, pressure, chemistry, or concentration, and the solution may be aqueous or a magma (or even a gas, as sulfur crystals may condense from vapors emitted by a volcanic fumerol, and snowflakes precipitate from air). A slow solidification or precipitation supports the growth of larger crystals. Note that this process is responsible for much of the mineral segregation that gives us ores, as well as all of the gemstones we admire. Crystals may be too small to see, as in agate, or incredibly large - see our Gypsum page for an astounding example. Of course, not all solids are crystalline. Very rapid cooling of a molten compound can result in a glass, where the individual molecules have random orientations, not the orderly arrangements found in a crystal.
Before the Earth was formed, before igneous or sedimentary or metamorphic rocks were even possible, there were primordial rocks and primordial minerals. In the early solar system these condensed directly from the solar nebula, and are visible today as asteroids and comets in space, and as meteorites on Earth. Indeed, the number of distinct minerals appears to have increased over time: see The Evolution of Minerals.
Amethyst Galleries' Mineral Gallery
describes over 600 mineral species (and varieties) and more than 5000 specimens
(see our new specimens last updated
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Our favorite specimens are marked with this symbol, and those that are still available for purchase are listed on our Favorites Page. Check out our new Minerals By Price pages, where you can easily find minerals under $10, between $10 and $20, or even over $1000!
We are having an Inventory Clearance Sale! Select specimens are from 10% to 50% or more off. See the By Name lists, and click on the Sale! links to jump to the first "on sale" specimen for each mineral. Or, see our By_Discount page which provides direct links to specimens at a given discount - your index to great bargains.
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To purchase our specimens, select a mineral using any of the indexes, and then choose the Specimens link (or use the specimens shortcut on the By_Name index). This will usually display several available specimens, some of which may be marked Sold or Sale Pending, but others will have an Add To Cart link which will add that specimen to your shopping cart. You may Cancel or Proceed to Checkout your order then, or after further browsing. Generally, you will return here to View Shopping Cart (if any), and from there you will Cancel it or Proceed to Checkout. Shipping is normally the next business day (with 3 to 5 days delivery time for most North America destinations). For more information (including our address), see the page How to Buy From Us.
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