Mineral identification basics
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Mineral Identification Basics. PHYSICAL PROPERTIES COLOR. Amethyst. Ionic Iron. Hematite Inclusions. Chlorite inclusions. Clear - Without Impurities. Quartz comes in a wide range of colors. It is very easily colored by even trace amounts of impurities. (*). Various colors of Quartz.

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Mineral Identification Basics

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Mineral identification basics

Mineral Identification Basics

PHYSICAL PROPERTIES COLOR

Amethyst

Ionic Iron

Hematite Inclusions

Chlorite inclusions

Clear - Without Impurities

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

Various colors of Quartz.


Mineral identification basics1

Mineral Identification Basics

INDICATIVE COLOR

Azurite (*)

Sulfur

Malachite

Turquoise

Rhodochrosite

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


Mineral identification basics2

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 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. (*)

Gold in Quartz


Mineral identification basics3

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

Specific Gravity =

(Weight in air) - (Weight in water )

(divided by)

(*)


Mineral identification basics4

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 basics5

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 basics6

Mineral Identification Basics

PHYSICAL PROPERTIES SPECIFIC GRAVITY

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. (*)

Balance is in “Balance” (*)


Mineral identification basics7

Mineral Identification Basics

PHYSICAL PROPERTIES SPECIFIC GRAVITY

NO Notches

(*)

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. (*)


Mineral identification basics8

Mineral Identification Basics

PHYSICAL PROPERTIES SPECIFIC GRAVITY

Selecting the right material. (*)

Opal in Rhyolite

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. (*)

Calcite with Garnet

Sphalerite

Limonite

Halite


Mineral identification basics9

Mineral Identification Basics

PHYSICAL PROPERTIES SPECIFIC GRAVITY

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. (*)

Opal in Rhyolite

Calcite with Garnet

Sphalerite

Limonite

Halite

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


Mineral identification basics10

Mineral Identification Basics

PHYSICAL PROPERTIES SPECIFIC GRAVITY

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. (*)

Opal in Rhyolite

Calcite with Garnet

Sphalerite

Limonite

Halite


Mineral identification basics11

Mineral Identification Basics

PHYSICAL PROPERTIES SPECIFIC GRAVITY

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

Opal in Rhyolite

Calcite with Garnet

Sphalerite

Limonite

Halite


Mineral identification basics12

Mineral Identification Basics

PHYSICAL PROPERTIES SPECIFIC GRAVITY

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. (*)

Opal in Rhyolite

Calcite with Garnet

Sphalerite

Limonite

Halite


Mineral identification basics13

Mineral Identification Basics

PHYSICAL PROPERTIES SPECIFIC GRAVITY

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. (*)

Opal in Rhyolite

Calcite with Garnet

Sphalerite

Sphalerite

Limonite

Halite


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Mineral Identification Basics

PHYSICAL PROPERTIES SPECIFIC GRAVITY

100 grams is too much.

Weight in air = 37.0 grams (*)

Determine the weight of the Sphalerite (*)


Mineral identification basics15

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 basics16

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 basics17

Mineral Identification Basics

PHYSICAL PROPERTIES SPECIFIC GRAVITY

0 grams

20 grams

7 grams

0.94 grams

Weight in Water (*)

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


Mineral identification basics18

Mineral Identification Basics

PHYSICAL PROPERTIES SPECIFIC GRAVITY

Weight in air

Weight in air

Specific Gravity =

Specific Gravity =

(Weight in air) - (Weight in water )

(Weight in air) - (Weight in water )

37.00 grams

37.00 grams

27.94 grams

Specific Gravity =

4.06

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 basics19

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 basics20

Mineral Identification Basics

PHYSICAL PROPERTIES MAGNETISM

MAGNETISMis 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 basics21

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. (*)


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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 basics23

Mineral Identification Basics

PHYSICAL PROPERTIES MAGNETISM

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


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Mineral Identification Basics

DOUBLE REFRACTION

DOUBLE REFRACTION:Isa 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 basics25

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 (*)


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