Azurite is one of the two most common copper minerals [the other being Malachite], and has been popular throughout the ages for its rich blue coloration.

It often forms small, druzy crystals that encrust a cavity or a crack in a rock, and can often be found with malachite, as in the picture above - the contrast between the blue and the green makes for strikingly beautiful specimens.

It is sometimes used in jewelry, but bright light, heat, and even exposure to air cause it to deteriorate, reducing the color. 

If heated, it will turn an ugly sort of black, which means that any sort of jewelry construction using azurite must be done at room temperature. It is also rather soft, and therefore easily damaged.

In the Middle Ages, azurite was commonly ground up and used for blue pigment in paints, as it was a more obtainable alternative to ultramarine [which was made from lapis lazuli]. 

Unfortunately, paints made from azurite tend to turn green as the years go by, so the colors in many of the famous old paintings we've all seen actually bear little resemblance to how they'd look if they were fresh!

A famous example of this is the Mona Lisa - click here to see the original along side the color-corrected version. It's quite a difference, isn't it?

Since lapis lazuli was primarily supplied from Afghanistan at the time, it tended to fetch very high prices. And as azurite was a common mineral throughout Europe, the flaws of azurite as a pigment were often overlooked.

Next time you look at a famous work of art, you could be looking at a little piece of mineralogical history as well.
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​ Here in Northern California, one of the more common collectible stones around is Actinolite. I've always had a soft spot for this mineral, ever since I was a child.

The name "actinolite" comes from the Greek word aktis, meaning "ray" - a reference to the appearance of the crystals.

It is a softer, more fibrous relation to Nephrite Jade, and can commonly be found in regions that have jade or serpentine. The crystals are usually green, ranging from pale green to nearly black - the coloration is determined by the amount of iron the specimen contains. More iron causes darker colors.

​In Mendocino County, California, actinolite can commonly be found in most rivers and creeks. The crystals will be worn smooth, but usually when you break them open, lovely bladed crystals will be exposed. When the sun is out, it can be easy to spot the specimens because of the way the sunlight reflects off each fibrous crystal blade - the rock seems to sparkle.

Translucent actinolite is rare, but can be faceted into gemstones if found in a sufficient quality.

A new location guide has been added -- Meridian, in Bosque County, Texas -- where you can find coral fossils, along with the heart urchins and gastropods common within the Comanche Peak formation of Central Texas.

A new collecting location in a new state! Come along for an overview of the fossil collecting outside of Mound, Coryell County, Texas -- where you can find large ammonites, gastropods, and cute little heart urchins.​

Druzy [also spelt druse or drusy] is a term used to describe a coating of very small crystals on another stone. Often, druzy crystals are found within small vugs or pockets in a stone. Sometimes, the crystals are so tiny you wouldn't even notice them but for a faint sparkle under a bright light.

The word can be applied to any different mineral that takes the form of these very small crystals - druzy quartz is probably the most common, but you'll find calcite, dolomite, and dozens of others exhibiting druzy crystals.

Have you ever looked inside a geode and seen a fine, tiny sparkle all around the bases of the larger crystals, that looked like someone had spilled a bit of glitter, or like frost on a sunny morning? Those were the druzy crystals.

Druzy crystals are frequently used in jewelry, usually in the form of a pendant displaying these tiny crystals. Sometimes the less appealingly-colored specimens are dyed, or covered with a metallic vapor coating - if you find metallic-looking druzy jewelry, be aware that they are probably not naturally formed.