Mineral 1 Flashcards
A ____ is a naturally occurring, inorganic, homogeneous solid, with a definite chemical composition, and an ordered crystalline structure.
Most _____ have
distinctive characteristics.
Some _____, however, are very similar that their
physical properties should be examined further to make a correct identification.
mineral
Geologists commonly use _____ such as color, streak, luster, crystal habit, cleavage, fracture, hardness, and specific gravity to identify minerals.
physical properties
___ refers to certain wavelengths of light that are reflected by the material, in this case, a mineral and is perceived by the observer.
-It is the most noticeable physical property of a mineral and is often the first thing that people consider when looking for minerals as gemstones for jewelry.
-However, using this as sole basis for mineral identification is not enough because different minerals can have the same __.
-In addition, color is highly affected by impurities or light diffraction. Mineral colors can be classified into idiochromatic, allochromatic and pseudochromatic.
Color
Self-colored minerals are called _____ minerals. Their color is a diagnostic property.
This means that the color of a mineral is constant and it depends on the elements that make up their chemical structure.
Examples are malachite (always
green), rhodochrosite (always red) and sulfur (always yellow).
idiochromatic
For _____minerals, color is not a reliable diagnostic property since small impurities may dramatically alter their color.
For example, quartz may occur in different varieties. This includes colorless, milky, smoky, citrine, amethyst, and rose as shown below.
____ minerals are often weakly-colored or colorless in their pure state, which allows impurities to pervade them with color. By contrast, idiochromatic minerals are strongly colored which drowns out any impurities in
color.
Allochromatic
Lastly, _____ minerals are false-colored minerals. Their colors are due to light diffraction. In this instance, color may be variable but is an exclusive roperties of the mineral.
pseudochromatic
The ____ is the color of the powdered form of a mineral. It is observed by rubbing the mineral across a streak plate.
-As shown below, the color of the mineral is not always the same as the streak color. For mineral identification, this property is more reliable than the color of the mineral since streak is always the same.
streak
_____ is the appearance of a mineral’s surface and is dependent on how it reflects light. Common ____ types are pearly, silky, dull, resinous, earthy, adamantine, vitreous or glassy, and metallic. Refer to the Fig. 5 and Table 1 for the description of each type.
Luster
____ is the characteristic shape in which a mineral grows and is a projection of the mineral’s crystal structure. Some common habits are acicular, blocky, tabular, fibrous, bladed, dendritic, and prismatic as shown below.
Crystal habit
_____ is the tendency of some minerals to break along flat surfaces.
These surfaces have the weakest atomic bonding which means that when you use a hammer to break a mineral, it will always break along this points.
______ surfaces tend to occur repetitively as parallel planes at crystal breaks, which constitute a set, or direction of cleavage.
Cleavage
____ is the pattern in which the mineral breaks aside from its planes of cleavage.
This happens when the atomic bonds are of equal strength. Unlike cleavage, fracture does not break along planes; it just breaks unevenly.
Various types of _____ exist in nature such as conchoidal, jagged, uneven and splintery.
Fracture
____ is the resistance of the minerals to scratching. It is measured by scratching the mineral with another object of known hardness.
For more accurate measurement, Mohs scale of hardness is used which is composed of ten minerals, numbered from 1 to 10 (1 as the softest and 10 as the hardest). The Mohs scale is a relative scale, not qualitative, which means that gypsum (H=2) is not twice as hard as talc (H=1), only that gypsum is harder than talc.
Hardness
____ is the ratio of a minerals’ weight to the weight of an equal volume of water. Therefore, a _____ of 4 means that a certain substance is four times heavier than water. The size of the mineral is independent of its _____. This means that a larger sample can still yield a smaller ______. The table below shows some of the _____ of common minerals. Notice that diamond, the hardest mineral, has a low _____.
Specific gravity
malachite (always
___), rhodochrosite (always ___) and sulfur (always ____).
green,
red,
yellow
The Mohs scale of hardness was named after its proponent, ____. Mohs was born on January 29, 1773, in Gernrode, Germany.
His early studies largely focused on Physics, Chemistry, and Mathematics but later on, he took advanced studies in the mining academy.
His interest in mineralogy was inspired by one of his
professors named ____.
In 1801, he became a curator of a private mineral collection owned by a banker named J.F. van der Null.
He was required to arrange the minerals into categories, so he started studying the different physical properties of these minerals.
He discovered the varying hardness of the minerals and later on designed a systematic classification of this property using a scratch test.
Carl Friedrich Christian Mohs,
Dr. Werner
