Clear - Without Impurities

Mineral Identification Basics• PHYSICAL PROPERTIES COLOR

Various colors of Quartz.

Hematite Inclusions Chlorite inclusions

Amethyst

Ionic Iron

Quartz comes in a wide range of colors. It is very easily colored by even trace amounts of impurities. (*)

Some minerals do have a certain color associated with them. Here are some examples: (*)

Mineral Identification Basics• INDICATIVE COLOR

Turquoise

SulfurMalachite

RhodochrositeAzurite (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

The SPECIFIC GRAVITY of a mineral is a measure of the mineral’s density. It is related to the types of elements that make up the mineral and how they are packed into the mineral’s atomic structure. (*)

Gold in Quartz

Gold has a Specific Gravity of 19.2. It is 19.2 times the weight of an equal volume of water. Water has a Specific Gravity of 1. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

The SPECIFIC GRAVITY of a mineral is determined by weighing the specimen in air and then weighing it in water. Here is the formula: (*)

(Weight in air) - (Weight in water )

Weight in airSpecific Gravity =

(*)

(divided by)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Triple Beam Balance

This is the equipment used in the lab at GCC to determine Specific Gravity. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

The first thing to check in using the balance is to make sure it balances at the zero mark when the tray is empty. (*)

This circle shows the zero mark and that the balance is calibrated correctly. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Balance is in “Balance” (*)

Notches (*)

NO Notches (*)Notice that the top three bars of the balance have notches. These are the positions in which the weights are REQUIRED to rest. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

The bottom bar has no notch. Instead the weight (the small chrome sleeve sitting over the zero mark on the left) simply

slides along this bar. It reads 0.1 to 0.01 grams. (*)

NO Notches (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Selecting the right material. (*)

Sphalerite

Opal in Rhyolite

Calcite with Garnet

HaliteLimonite

Not just any mineral will do. In determining the specific gravity of a mineral it must be pure, free of pockets or cracks (places that can trap air) and it should not easily dissolve in water. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Sphalerite

Opal in Rhyolite

Calcite with Garnet

HaliteLimonite

The Limonite is full of pore spaces. It is almost like a sponge. When it is weighed in water it has numerous trapped air pockets that will make it lighter that it should be. (*)

It would be difficult to get an accurate weight. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Sphalerite

Opal in Rhyolite

Calcite with Garnet

HaliteLimonite

This is not a pure specimen. It is a combination of two minerals. The result of the specific gravity process would only give you an average of the two minerals. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Sphalerite

Opal in Rhyolite

Calcite with Garnet

HaliteLimonite

The opal in rhyolite has the same problem as the calcite with garnet. It is not a pure sample (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Sphalerite

Opal in Rhyolite

Calcite with Garnet

HaliteLimonite

Halite is a salt. When weighed in water it dissolves. It would be difficult to get an accurate reading as it would become lighter and lighter as it slowly dissolved. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Sphalerite

Opal in Rhyolite

Calcite with Garnet

HaliteLimonite

Sphalerite (pronounced: sfal er ite) is a good choice. It is a pure sample with no crack or pore spaces. And, it does not dissolve in water. (*)

Sphalerite

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Determine the weight of the Sphalerite

(*)

100 grams is too much.

Weight in air = 37.0 grams (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Weight in Water

The weights are in the same place but now that the sphalerite is submerged in water it is lighter, and the balance is again out of balance. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Weight in Water

It is important to note that the specimen being weighed is not resting on the bottom of the beaker or touching its sides. It is also completely submerged beneath the water. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

Weight in Water (*)

0 grams

0.94 grams

7 grams20 grams

The weight of the sphalerite in water is 27.94 grams. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES SPECIFIC GRAVITY

(Weight in air) - (Weight in water )

Weight in airSpecific Gravity =

(Weight in air) - (Weight in water )

Weight in airSpecific Gravity =

37.00 grams

27.94 grams37.00 grams

4.06Specific Gravity = Note that there are no units. The grams cancel out. This is a ratio of how heavy the mineral is compared to an equal volume of water. The sphalerite is 4.06 times heavier than water. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES TASTE

IT IS NOT RECOMMENDED THAT A TASTE TEST BE PERFORMED ON MINERALS AS A STANDARD PROCESS. SOME MINERALS ARE TOXIC.

However, the mineral HALITE is common salt and has a unique taste. (*)

Halite cubes from Trona, CA (*)

Mineral Identification Basics• PHYSICAL PROPERTIES MAGNETISM

MAGNETISM is the ability of a mineral to be attracted by a magnet. This most commonly is associated with minerals rich in

iron, usually magnetite. (*)

This is a piece of MAGNETITE with a magnet adhering to it. Magnetite is a mineral that is strongly magnetic in that a magnet will easily be attracted to it. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES MAGNETISM

More sensitivity is achieved if instead of a large sample, small pieces are used. In this way, even weakly magnetic minerals will be attracted to the magnet. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES MAGNETISM

This is a sample of “black sand” from Lynx Creek, Arizona. Its dark color is due to its high concentration of magnetite. See what happens when a magnet is place beneath the bottom right portion of the paper. (*)

This technique is used to separate out much of the unwanted material in the search for gold in placer deposits. (*)

Mineral Identification Basics• PHYSICAL PROPERTIES MAGNETISM

LODESTONE is a variety of Magnetite that is naturally a magnet. (*)

Mineral Identification Basics• DOUBLE REFRACTION

DOUBLE REFRACTION: Is a property shared by many minerals ( but not those in the isometric crystal system). It is produced by the separating of a beam of light as it passes through the crystal structure. It is best displayed in the mineral CALCITE. This image clearly shows the double image below the calcite. (*)

Mineral Identification Basics• CHEMICAL PROPERTIES

REACTION TO HYDROCHLORIC ACID

Some minerals, notably the carbonates, react to cold dilute HCl. In this illustration a piece of CALCITE is shown to react (fizz) after HCl is applied. (*)

Calcite Reacts to HCl (*)