Geology Facts

MOHS HARDNESS SCALE

Mohs Scale was established by German mineralogist Friedrich Mohs to help identify minerals by their hardness. Minerals with a higher number will scratch those with a lower number. CAUTION: Never use a good specimen to test hardness as it will leave a permanent scratch.

1. Talc

2. Gypsum Examples: Amber

2.5 (fingernail will scratch) Examples: Gold, Silver, Some Jet

3. Calcite

3.5 (coin will scratch)

4. Fluorite Also: Rhodochrosite, Malachite & Azurite, Some Jet & Some Pearls

5. Apatite

5.5 (glass will scratch) Examples: Rhodonite, Lapis Lazuli, Some Opals, Turquoise, Jade, Rhodonite

6. Feldspar Examples: Labradorite, Amazonite, Sunstone, Moonstone

6.5 (steel knife will scratch) Examples: Garnet, Some Opals, Some Olivine, Hematite

7. Quartz Examples: Agate, Chalcedony, Onyx, Bloodstone, Chrysoprase, Jasper & Carnelian, Some Olivine, Amethyst, Citrine, Tourmaline, Zircon

8. Topaz Examples: Spinel, Some Emeralds and other Beryl's

8.5 (emery cloth sill scratch) Examples: Chrysoberyl

9. Corundum Examples: Ruby, Sapphire,

10. Diamond

THE FAMILY TREE OF MINERALS

Many minerals are related to each other in their chemical composition. However they have been given different names to describe various color combinations and markings that are created as the molecules were arranged differently during growth. Below are some of the common mineral groupings and what the different names are for each mineral according to their color or individual properties.
Beryl Family FAST FACT: Emeralds were mined in Egypt in 1500 B.C. and Cleopatra is said to have possessed an emerald engraved with her portrait. Today, the best source for Emeralds is Columbia.	Aquamarine=Light blue-blue green, Morganite=Rose pink, Golden Beryl=Golden yellow, Heliodor=Yellow to yellow green, Goshenite=Transparent, Bixbite=Red, Bazzite=Blue, Emerald=Green
Corundum Family FAST FACT: Corundum is the second hardest gem behind diamonds. In fact, a high quality Ruby is more valuable than an equally sized diamond.	Red=Ruby, Sapphire=Blue, green, yellow, Star Rubies & Sapphires=display star like sheen known as asterism. Formed by tiny needle thin inclusions of rutile in the stone.
Cryptocrystalline Family FAST FACT: Jasper is made up of Chalcedony, Quartz & Opal. In Ukraine, boulders of jasper have been sculpted into beautiful objects.	Agate=Thin parallel bands in varying colors, Bloodstone or Heliotrope=Dark green with numerous red spots, Chrysoprase=Bright apple green, Jasper=Red, green, brown, Carnelian=Rusty orange, Onyx, Chalcedony=Pale blue or yellow, Sard=Reddish brown, Plasma=Dark green, Lingam=Brown with red markings
Feldspar Family FAST FACT: Make up 50% of the earth's crust and 5 times more common than quartz	Amazonite=Green with white striping, Sunstone=Flake like inclusions of hematite and goethite, Labradorite=grey plagioclase iridescent sheen, Orthoclase=golden yellow
Garnet Family FAST FACT: Pyrope is the most popular form of Garnet. However many garnets are not gem quality and are used worlwide as abrasives.	Almandine=Red to violet red, Spessartite=Yellow, rose or reddish brown to orange, Pyrope=Deep red, Grossular=White, yellow, lime, orange, black, brownish red, Andradite=Colorless to brown and black and yellow green, Demantoid=Emerald green
Jade Family FAST FACT: Jade is made up of microscopic interlocking crystals. They can withstand great pressure and are more elastic than steel.	Nephrite=Black, dark green, brown, yellow and white. Jadeite=Green, yellow, white, pink, purple, orange, bluish, brown or gray. Imperial Jade=The most prized and sought after emerald green shade of jadeite.
Meteorite Family FAST FACT: Because most land in water or in deserts, only around 10 of the thousands of meteorite strikes that occur each year, are recorded.	Siderites=Nickel and Iron in dark parallel bands, Aerolites=Silicate material consisting of Pyroxene and Olivine, Stony Irons=Composed of metals and silicates, Tektites=Molten meteoritic and crustal in composition
Opal Family FAST FACT: The "play of color" seen in an opal is created by silica beads that reflect and diffract white light. The larger the beads inside, the greater color spectrum will be seen.	Black Opal=Black, most prized, White Opal=Milky, Fire Opal=Red, Water Opal=Colorless
Quartz Family FAST FACT: Rutile inclusions are common. Hardness of 7 or more is what we consider to be a "precious" gem.	Colorless=Rock Crystal, Violet=Amethyst, Yellow=Citrine, Brown to Black=Smoky, White=Milky, Pink=Rose, Blue=Sapphire Quartz, Black=Morion
Tourmaline Family FAST FACT: If both terminations are present and the crystal is heated, the ends become positively and negatively charged.	There are 7 distinct varieties of Tourmaline. Schorl=Black, Elbaite=Variety of colors, Dravite & Buergerite=Brown, Rubellite=Pink, Chromdravite=Green, Uvite=Black, brown, yellow-green. Also quite prized is "watermelon" Tourmaline, known for having both green and pink colors along the length of one crystal.