Optical Mineralogy

CHAPTER I
INTRODUCTION
1.1. Background

              Mineral is a substance or chemical elements, chemical combination or a mixture of inorganic chemical combinations, as a result of physical processes and specialty chemicals naturally. Mineral is a homogeneous material and has a specific chemical composition or formula. When conditions permit, got a suitable structure, in which the shape of the crystals and determined their physical properties. Earth is composed of several types of rocks and rock composed of minerals and small amounts of other materials such as organic matter. Itself consists of mineral elements are mixed. Element in this case is a matter that can no longer be separated chemically. Atom is the smallest particle of an element that has the properties of the element and are too small to be seen even under a microscope.

              The observations made one of them a mineral observations through nikol nikol cross and parallel and penganatan konoskop. This observation is very important because in this observation will be known optical properties of minerals, so it can be determined from observations of the mineral name. Some of the above are the background factors execution event practicum and nesosilikat inosilikat minerals.
1.2. Aims and Objectives
The purpose of this lab is to apply what is obtained in the process of learning or lectures. While the objective of this lab is expected praktikan can:
1) Determining the optical properties of minerals in parallel observation nikol, nikol cross and observations konoskop
2) Determine the mineral name of the optical properties of the observed
3) Can distinguish between observations parallel nikol, nikol cross, and observations konoskop
4) Being able to determine the optical properties of minerals were observed between the mineral and Philosilikat inosilikat.
1.3. Equipment and Materials

               Tools and materials used in this practicum are:
1. A4 paper
2. Lab worksheet
3. Stationery
4. Lap rough
5. Soft cloth
6. Polarizing microscope
7. Incision mineral
8. Colored pencils
9. Practical guidance
1.3. Work Procedures

 Working procedures in parallel and observations ortoskop nikol nikol cross to determine the optical properties of minerals are as follows:
a) Laying the polarizing microscope on the table by holding the arm Polarization Microscopy sedemikana way that the microscope was before the User.
b) Menyentringkan microscope
c) Determine the sample sequence number
d) Determine the number of props in a way malihat number on mineral samples observed
e) Determine the magnification of the objective lens, ocular lens magnification and total magnification lenda malihat by objective and eyepiece.
f) Determine the number scale
g) Determining mineral position (X, Y) position by looking at the mineral scale abscissa axis and the axis of ordinate
h) Determine the size of the mineral with a long way to determine the mineral by using the yarn cross-scale (mm) then the result is multiplied by the number scale
i) Determine the mineral colors by colors that appear directly observed on the microscope
j) Determine pleokroisme by observing changes in the mineral color or nikol nikol ortoskop without parallel when the object table rotated 90o. Pleokroisme weak if differences occur in contrast color
k) Determine the intensity
l) Determine the refractive index of minerals by way of:
1. Cover part of the entry of light into the mineral by using opaque objects
2. When the dark shadow appears at the position opposite to the direction of the position of the lid, then n min <n cb
3. Conversely if it looks dark shadow appears at the position in the direction of arrival of light cover, then n min> n cb
m) Determine the mineral parts in a way: if the minerals are in the form of straight lines parallel to each other then cleavage in one direction
n) Determine mineral fractions in the following manner:
1) If the fractions showed a surface wave in the curved pieces are concoidal
2) If the surface shows pecahanya broken into small fragments with a field that is still close to the data field is even pecahanya
3) If the fractions showed an irregular surface with the pointed ends of the pieces are hackly
4) If the coarse fraction by fraction showed an irregular surface with the pointed ends of the pecahanya is uneven
5) If the fine fraction which showed broken into small sharp threads or fibers resembling the pieces are splintery
o) Determine the form of minerals by way of:

                                            I. Looking at the form of the mineral with two-dimensional conditions

                                         II. If the crystal is limited by the crystal itself bidnag the mineral forms euhedral

                                       III. If the crystal is limited by the crystal itself then forms subhedral mineral

                                      IV. If the crystal is not at all limited by its own crystal fields then forms anhedral mineral
p) Determining mineral relief in a way: the greater the refractive index, the higher the mineral relief.
q) Determining mineral inclusions
r) Determine W.I. maximum mineral
s) Determine the double refraction of mineral
t) Determining mineral twinning
u) Specifies a dark corner dengen ways:

                                            I. Rotate the object table to the left until the maximum light and record the scale noniusnya

                                         II. Rotate the object table to the right again until dark noniusnya scale maximum and record
v) Determine the type of darkness in a way:
1. If 0o or 90o angle dark, then dark is gelapa parallel (parallel).
2. If the angle 45o dark, then dark dark dalah symmetric
3. If the dark corners 1o-44o or 46o-89o then the darkness is dark slant.
4. If the dark corner of the dark wavy 3o.
w) Determine TRO by:

                                            I. Comparator insert pieces cast

                                         II. If symptoms occur addition, the position of the axis images indikatrik mineral

                                       III. Looking at the position of the axis to the long axis indikatrik mineral mineral crystallographic

                                      IV. If Z equal or less than 45 ° to the long axis crystallographic, then the sign of its optical range is length-slow

                                         V. If the X axis is parallel or 45o to the long axis of the crystallographic, then the orientation is length-fast
x) Determine the optical axis
y) Determining optical mark mineral
z) Determining the interference image:

                                                            I. Determination isogir

                                                         II. Determination of color bracelet

                                                       III. Determination of 2V angle
aa) Specifies the name of the mineral.
CHAPTER II
LITERATURE REVIEW
2.1. Silicate structures

                Class of silicate minerals which are important given that 25% of the minerals known to form silicates. They make up 90% of the lithosphere. Basic unit of all the silicate structure is tetrareader where Si atoms are surrounded by 4-O atom. tetrareader in balls-O with a radius of 1.32 AE (Angstrom units) are ion-Si +, with a radius of 0.39 AE.
Brupa silicates lattice ions (ionentralies), where the anion-anion Si-O or Si-O-Al, while cation-cation elements are electro-positive. It has long been known that the ratio of Si: O in silicate can have various values. In silicates, then tetrareader-SiO4-tetrareader can be in 4 different ways:
a. In the cluster-cluster.
b. In the form of a chain.
c. In the form of layers.
d. In the form of three-dimensional lattice structure.

               Strunz (1941) divides silicates in several categories, namely:
1. Inosilikat
2. Nesosilikat
3. Tektosilikat
4. Sorosilikat
5. Phyllosilikat
6. Siklosilikat.
In this particular discussion will discuss about Inosilikat and Philosilikat.
1. Inosilikat

              Inosilikat (Chain Structure) (inos = fibers) which tetrareader-tetrareader-SiO4 chains forming a low and not limited in length. If two of the oxygen used together in a way to make one long chain of connected SiO4 tetrahedra, we got a chain silicate or inosilikat. In this case the basic structural unit of Si2O6-4 or SiO3-2. This group is the basis for piroksin group minerals, such as orthopiroksin (Mg, Fe) SiO3 or klinopiroksin Ca (Mg, Fe) Si2O6.

                 There are two kinds of one-dimensional expansion consisting of tetrareader-tetrareader-interconnected SiO4.
1) The chain SiO4 single / simple

                  Here is an overall chain length of a crystal. Examples of minerals are:
a. Group amphiboles
· Anthophyllit
· Series tremolo-actinolit
a. Tremolit
b. Actinolit
c. Hornblende series
d. Hornblende
e. Arfvedsonit
b. Class piroksin
a) Series enstatit
b) Enstatit
c) Hyperstene
d) Series diopsit
e) Diopsit
f) Augit
g) Aegirit
h) Jadeit
i) Spodumen
Rhodonit MnSiO3
Wallastonit CaSiO3
Pectolit Ca2NaSiO8 (OH)
Chrysocolla CuSiO3.2H2O
2) The chain SiO4 plural / dual
This situation is found in amphiboles-amphiboles (Si4O11) 6 -. Ribbons-connection here is the connection of (SiO4O11). In terms of-6 formed ions are enough places for the O-OH clusters that do not require a wider than ion-ion-O (1.32 AE) but also for ion-F "where the radius of 1.33 AE. When Al occupy the majority rather than place it in the Si crystal lattice will be bound positive ions are monovalent ions such as K, so it will be neutral again earlier crystal lattice properties.
The corners of the slit at 87o and 124o piroksin-piroksin on amphiboles-amphiboles, is determined by the type / kind of different chain this. This situation runs parallel to the c-axis kristalografis. Chain relationships with each other are connected metal. This binder turned out to be weaker than the bonds that chain-field splittings SiO4 always occur between the chains. (See figure 2.3)
2. Pilosilikat
v serpentine group
Ø antigorit - Mg3Si2O5 (OH) 4
Ø Krisotil - Mg3Si2O5 (OH) 4
Ø Lizardit - Mg3Si2O5 (OH) 4
v Group clay minerals
Ø Haloysit - Al2Si2O5 (OH) 4
Ø Kaolinite - Al2Si2O5 (OH) 4
Ø Ilit - (K, H3O) (Al, Mg, Fe) 2 (Si, Al) 4O10 [(OH) 2, (H2O)]
Ø montmorillonite - (Na, Ca) 0:33 (Al, Mg) 2Si4O10 (OH) 2 · nH2O
Ø Vermiculite - (MgFe, Al) 3 (Al, Si) 4O10 (OH) 2.4 H2O
Ø Talc - Mg3Si4O10 (OH) 2
Ø Paligorskit - (Mg, Al) 2Si4O10 (OH) · 4 (H2O)
Ø Pirofilit - Al2Si4O10 (OH) 2
v mica group
Ø biotite - K (Mg, Fe) 3 (AlSi3) O10 (OH) 2
Ø Muscovite - KAl2 (AlSi3) O10 (OH) 2
Ø Flogopit - KMg3 (AlSi3) O10 (OH) 2
Ø Lepidolit - K (Li, Al) 2-3 (AlSi3) O10 (OH) 2
Ø Margarit - CaAl2 (Al2Si2) O10 (OH) 2
Ø glauconite - (K, Na) (Al, Mg, Fe) 2 (Si, Al) 4O10 (OH) 2
v klorit
Ø Chlorite - (Mg, Fe) 3 (Si, Al) 4O10 (OH) 2 • (Mg, Fe) 3 (OH) 6
3.
2.2. Observations Konoskop

               Konoskop appearance is light on convergent light, because light condenser lens will yield mengkuncup that produces a point-focused mineral incision. The light then passes through a crystal incision and then captured by the objective lens.
1. Optical axis

             Terpolarisir light passing through anisotropic minerals, will be refracted into two rays that vibrate in all directions with different speeds. But at the direction of a particular slice of the light is refracted in all directions with the same speed. Perpendicular to the direction of the incision di.kenal as optical axis.

             At minerals bersisitim tetragonal crystals, hexagonal and trigonal indikatrik there are two axes (axis vibrating beam direction), ie the axis of the beam ordiner (regular) and extra light ordiner (excellent). At bersistim mineral crystal, there is only one possible direction of the incision, which refracted light vibrates in all directions at the same speed. Therefore, the minerals bersistin tetragonal crystals, hexagonal and trigonal axis Optics have one (uniaxial). While the minerals crystal bersistim orthorombik, nonoklin and there are three kinds triklin indikatrik axis, ie the axis of the X-ray indikatrik (fastest), Y rays (intermediates) and Z-rays (palinglambat). in these minerals, there are two possible directions of the incision, which refracted light vibrates in all directions at the same speed. Therefore applying minerals such crystals have two optical axis (biaxial).
2. Optical mark
Ø Signs Mineral Optical Axis One

               Ordiner light speed and extra ordiner on one crystal axis (uniaxial) is not the same. Extra light on certain mineral ordiner ordiner faster than light, but on the other mineral ordiner rays can be faster than light ordiner extra. To facilitate the discussion of diversity made a deal that uniaxial minerals that have extra light ordiner faster than light ordiner Optical Negative Marking. In contrast to uniaxial mineral having light faster than light ordiner ordiner Extra Optical Marking Posltif.
Ø Signs Two-axis Optical Minerals

               On two axes mineral, speed X-ray, light beam Y and Z are specified, meaning that on each mineral X-ray is the fastest ray, Y ray is a ray of light intermediates and Z is the slowest rays. The only difference between each other is mineral kedudukkan / indikatrik axis position of the rays associated with Line For Angle Optical Axis. Two axes mineral Optics Positive Signs nempunyai said, if the Z axis coincides with the beam indikatrik Line For Angle Taper (BSL) or Acute Centred Bisectrix (BXA) and the axis coincides with the X-ray indikatrik Line For Angle Blunt (BST) or obtuse Centred Bisectrix (Bxo ). Conversely, if the Z axis coincides with the beam indikatrik Line For Angle Blunt (BST) and the axis coincides with the X-ray indikatrik Line For Taper angle (BSL), the mineral has a negative optical sign.
3. Optical axis angle (2V)

             Optical axis angle (2V) is the angle formed by the two optical axes. therefore the optical axis angle is only found in two mineral axis. in particular incision, with regard lnterferensinya images, can be calculated magnitude of the optical axis angle.
4. Picture Interference Crystal Axis One (uniaxial) and Determination of optical mark.

              There are some pictures kenampakkan interference on one crystal axis. Kenampakkannya is highly dependent on the direction of the incision to the optical axis.
Picture Interference Centralized v
v There is the incision that its optical axis perpendicular cut (incision isotropic).
v Shows isogire with four arms, and melatop exactly in the middle.
v Memperilhatkan color bracelets (isofase), the number of these bracelets are very dependent on the price of the double refraction of each mineral. The greater the price of the double refraction, the more color bracelets.
v If a table object rotated 360 °, the image interference does not change at all
How To Determine Signs Centralized Optical Image Interference
a. Extraordinary ray component is always vibrating in a field that cut the field of view as the radius.
b. To determine whether the extraordinary ray is a ray of slow or fast, then the comparator used.
c. If quadrants l and 3 show symptoms adduct (blue color), while quadrants 2 and 4 showed symptoms of subtraction (yellow-orange) means a light beam incredible slow, the crystal has a positive optical sign. Conversely, if the quadrants l and 3 show symptoms subtraction, quadrants 2 and 4 show symptoms addition, the mineral has a negative optical sign.
5. Picture Interference Not Centered.
Crystals contained in the incision which cut oblique to the optical axis.
Melatop may not be visible (but not in the middle).
Determination of optical mark with centralized interference image, but must first determine the position of each kwadrannya.
6. Picture Interference Optical Axis
· There is the incision is cut perpendicular to the optical sb.
· Ask one arm visible isogir.
· Isogir against the immovable object table movement.
· Pictures of interference is best to determine the optical axis angle (2V).
Determination Signs Optical Image Optical Axis Interference
Ø In the two axes mineral applicable provisions of that sign is positive if the optical light beam coincides with Bsl is Z, and the optic sign is negative if the beam is coincident with the X-ray Bsl (Bst coincides with Z-rays).
Ø Direction Y vibrating beam is always perpendicular to the optical axis of the plane (BSO). Then the interference image beam optical axis vibration direction Y is a tangent of isogir.
Ø rays are the rays that vibrate and light Y coincides with Bst (because the incision is Bst an angle less than 45 ° to the object so that the incision rotary table position isogir diagonal
Ø Enter the comparator and observe changes in interference colors isogir convex side.
Ø If symptoms occur then the addition of Y-ray beam which is faster, which means more light vibrating perpendicular to it is the slower the light beam Z
Ø Thus Z beam coincides with Bst, the optical sign is negative.
Ø subtraksi Conversely if symptoms occur, then the positive optical sign
CHAPTER IV
CLOSING
4.1. Conclusion
From the results of lab work that has been done, it can be concluded that:
1. At this pengamata, made 3 kinds of observations are:
a. Nikol observations parallel optical properties observed were pleokroisme, intensity, refractive index, parts, pieces, shapes, reliefs, and inclusion.
b. Observations nikol cross the optical properties of the observed interference colors maximum, double bias, twin, dark corners, and kind of dark.
c. Konoskopik observation that the optical properties of the observed optical axis, the optical signal, and the interference image that includes isogir, color bracelets, and 2V angle.
2. the observation of this mineral is known that the name of the object of observation minerals are minerals Quarsa and Leucit
3. The difference between observation parallel nikol, nikol cross and observations konoskop ie parallel to the observation nikol not mengginakan konoskop anslisator and on observations using the observation konoskop analyzers while using pinhole and Lesa Betrand amici that the parallel observations and nikol nikol cross is not used.
4. The difference between mineral and nesosilikat inosilikat namely:
a. At inosilikat mineral has cleavage 1 direction, uneven fractions, whereas the mineral has no cleavage and nesosilikat fractions.
b. In the dark corner of mineral inosilikat smaller than in mineral nesosilikat.
c. Bracelet color on the mineral inosilikat weak double refraction, while the mineral color bracelet nesosilikat strong double refraction.
4.2. Suggestion

              After participating in this event practicum there are some suggestions that we would like to give as a practitioner, such as:
1. While doing practical observations should be given the opportunity to take pictures of the current appearance of both microscope observations parallel nikol, nikol cross and at the time of observation in order to expedite the process TRO asiatensi
2. To an assistant who was unable to perform on the practitioner assistance that can would be able to communicate the assistant coordinator so that the learners do not feel disadvantaged by reason of gathering reports