Jan 052018
 
Help in appraising diamonds and gemstones. Interesting.
File GEMOLOGY.ZIP from The Programmer’s Corner in
Category Financial and Statistics
Help in appraising diamonds and gemstones. Interesting.
File Name File Size Zip Size Zip Type
GIA.BAS 45501 20102 deflated
GIA.BAT 12 12 stored
LINE.DOC 6272 2302 deflated
MORE.COM 384 264 deflated
PRINT.BAT 22 22 stored
READ.BAT 22 22 stored
README.DOC 21172 7972 deflated
STONE.BAS 53745 16484 deflated

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Contents of the README.DOC file


Gemologist Integrated Appraisal.BAS

This program was developed by Robert Williams, GG. of Florida
Professional Appraisers, 249 Carolina St. Ft. Myers Beach, Fla.
33931. as a help in order to alleviate error in math and to do
the routine table look up work usually done by gemologist doing
appraisals. It was expanded to cover gold and silver.
It also can be used to buy and sell Gold, Silver, Diamonds, &
Colored Stones. If the numbers do not agree with your experience,
the multiplier used just before the output of the final figure
can be changed. (as it must be when prices and/or inflation
change).

Please make any changes you think will help, but if you give a
copy to another please use the latest official release, not an
altered one. If you think the changes or corrections are needed
by everyone send the corrections and changes to the above address
and they will be considered for inclusion in the next release,
(with credit to you). I am particularly interested in expanding
this program to include a print out by the colored stone portion
similar to the Diamond section and/or printing out an appraisal,
but so far this seems impractical as each appraisal is unique.

If you find a use for this program or think it worth expanding
send $ 35.00 to Florida Professional Appraisers at the above
address. For your money you will receive an explanation as to how
to change the figures to match changes in prices due to inflation
etc., and if I get a good response, I will be driven to make this

into a professional quality program.

This file contains a listing of Diamond prices as of 12/86,
most jewelers use this type of list, but most trained
Gemologists use the reduction method of arriving at a value.
This release (6) was up to date as of 12/86.

Always remember to double check everything - and remember
Diamonds are often sold by negotiated price as are colored
stones.

When I first became a Gemologist I still had a problem getting
information on prices, retail prices vary a lot depending on
overhead and many other factors. Wholesale prices vary less but
still they are not the same from one wholesaler to the next, so
the question is, what is the value ? One can only do as
appraisers do all over the world, that is get all the information
you can and give a weighted average as the value. This program,
even when fine tuned, (all output agrees with current prices), is
only one source, and, (even our own), is never used without
checking others.



This program is based on accepted methods of diamond grading and
evaluation. The relationship between stones, should remain the
same over a long period of time and should not be changed except
on careful consideration, (lines 2080-3480). The value (wholesale
line 1130) is easily changed by changing the multiplier in the
same line, ie:Q=P*K:Q=Q*10: IF IN YOUR EXPERIENCE the wholesale
price is too high, change the number multiplied times Q to a
smaller number, and if the wholesale price is too low change it
to a higher number. This will change all the output to reflect
the new price across the board. If the prices of only a certain
sector of the Diamonds are different (all the larger stones are
over priced, or all of the stones under 1ct. are underpriced),
you must change the value of "L" in lines 1450-1720. Example all
of the Diamonds over 4cts are twice too much. Change the value of
L in line 1720 to L=600, or whatever.



This short description of Diamond grading is not intended to be a
tutorial nor an instruction. The following information has been
oversimplified and understated, but it might help to whet the
appetite of someone just getting interested in diamonds and
colored stones. Robert J. Williams, GG

Specific Gravity: SG: Density or Specific gravity is valuable in

the determination of the identity of an unmounted stone. Formula:



weight in air
------------- = specific gravity
weight in air - weight in water

there are also liquids that help to determine the approx.
specific gravity that are made with Clarici's solution.

Refractive Index: RI: When a beam of light passes from air into
another transparent material as a gem, its velocity is reduced
and the beam is bent, unless it strikes at 90' to the surface.
This is its refractive index. This can be measured by an
instrument known as a refractometer.

Weight = Carat = .200 gram = 200 milligram

Cut = make: In this program, true to accepted methods, all
Diamonds are graded down from the Ideal cut. table = 53% ; crown

= 34.5% ; pavilion depth 43.1% ; pavilion angle 40.75%



Girdle: widest part of the stone.

Culet: bottom point of the stone. sometimes blunt and very large.

Hardness: H: There are several man made materials that can be
used to test hardness.

Silicon carbide - 9.5
Hardened steel - 6-7
Ordinary Glass - 5.5
Copper penny - 3

Standard hardness scale for minerals:

Diamond - 10 Apatite - 5
Corundum - 9 Fluorite - 4
Topaz - 8 Calcite - 3
Quartz - 7 Gypsum - 2
Feldspar - 6 Soapstone- 1

Caution: Any unknown scratched with a point or an edge drawn
across another material, is dangerous, it is very easy to mar the
surface or chip or break the stone.

Clarity grades: Diamond:

VVS - Very Very Slight inclusions, (imperfections), very
difficult to locate by a trained examiner with a corrected 10x
loupe.

VS - Very slight inclusions visible to a trained eye with a 10x
loupe.

SI - Slight imperfections not usually visible to the naked eye.

I - Imperfect, some of which are visible to the naked eye in
strong light.

Each of these grades are further divided. ie: Flawless,
VVS1,VVS2,VS1,VS2,SI1,SI2,I1,I2,I3,I4.

Color grades:

D E F - Colorless to tyro and when mounted very difficult for
expert to tell dif. in grades.

G H - Very Very slight tint

I J - Unmounted Stones are beginning to show a hint of color to
untrained persons with good color vision.


K L - Stones are now showing a hint of color when mounted.

M N - yellow tint can be seen by most persons.

O - Z yellow and fancy colors

Recommended :
Classes and Equipment: Gemological Institute of America
1660 Stewart St.
Santa Monica, CA.
90406

Books: Handbook of Gem Identification
by Richard T. Liddicoat, Jr.

Gem Testing
by B W Anderson, B.Sc., F.G.A.

Color Encyclopedia of Gemstones
Joel E. Arem Ph.D.,F.G.A.



GIA.BAS

I am going to attempt to walk you through a simulation using this
program. The program has limited uses to anyone except a person
with the knowledge of terms and an access to the proper
instruments used in measurements of refractive index, microscope,
scales (grams), polariscope, dichroscope, professional color
grading Diamonds, hardness testing kit, and specific gravity
test. There are other instruments needed at times. However, for
the purpose of this simulation we will assume you have some or
all of the information needed to complete a run.

First, lets take a loose Diamond, you look at it, it is round and
faceted, it has 57 facets, more or less, you measure across the
Diamond, across the widest point, (at the Girdle), it measures
4.2 mm. (all stone measurements will be in millimeters), you then
measure from the top, (table) to the bottom, (culet) this
measures 2.4 mm. then you measure across the table, (top), from
point to point and it measures approximately 2.5 mm.

Now you have enough information to have the computer give you the
weight (Cts.) of the Diamond.







Start the program and you will get a main menu showing the first
item Diamond value. select 1 and hit enter. a question will
appear "Do you know the size ? (of the Diamond in Cts), enter "n"
and hit enter. (after each answer you must hit the enter key, I
will not state this hereafter). Now the question is "Depth in
mm?" this is where you enter your "2.4" (without quotes), then
you get the question "Diameter?" enter "4.2", then you get the
question "table diameter?" enter "2.5". Now you see "girdle
thickness?" this is a judgment call and only experience will
tell you the correct answer to input, but for this simulation
enter "0". Next you will see "Table Deductions =5" and "Depth
Deductions =5", this is information of interest to a Gemologist
only, ignore for now. next you will see a question "Total finish
deduction ?" again this is a judgment call on each stone, but
for now enter "0". You will now get a message stating corrected
weight is .222 cts. (if everything was entered as above). This is
the weight of the Diamond as if it had been cut to the most
desirable proportions, (no deductions). you will now get a base
price (ignore) next a question "Clarity VVS=1, VS=2, SI=3, I=4"
this is a subjective judgement by a trained gemologist as to
where, how large, and how many inclusions there are in the
diamond under a 10x hand held loupe. For the purpose of this
simulation this short explanation of internal quality is offered.
VVS= very,very slight imperfections, very difficult to locate by
a trained examiner at 10x. VS= Very slight imperfections not
visible to the naked eye but easily observed at 10x. SI= Slight
imperfections not visible to the naked eye but easily visible
under any magnification. I= Imperfections visible to the naked
eye. The above grades are simplified and there are other grades
between each of these but for now....enter "3"(SI)
the next question is color..DEF=1, G/H=2, I/J=3, K/L=4
Now this is the most subjective of all, in order for one to
correctly judge the color of an unmounted Diamond, one must have
other Diamonds with which to compare, That is comparison stones
already graded as to known colors and certified. The Diamond
color grades go from "D" colorless to approx. K/L where most
people will be able to see a hint of color, and to z where the
world of fancy colored diamonds end. but for our simulation we
will assume I/J (3) so enter 3.
At this point you will get some messages and the wholesale value
of the stone, (based on some U.S. wholesale prices)
next the question of "Do you want a review of values ?" in our
test enter "1"
Now.... the results of all that work.... you get all of the
previously entered information and the value of the diamond at
different hypothetical levels of sale. the cash value is what you
would want to give on pawn, for instance. a 2x markup would be
the avg jewelry store, 3x would be a carriage trade jewelry
store, and wholesale is what they would be expected to pay for
that stone. a discount jewelry store might be .5x.


The way to test this program and it values is to take a Diamond
that is for sale or has been sold recently and enter all of the
information from its appraisal into the computer and see if you
get within 10 % on the level of the appraisal, ie:appraisal
Retail Replacement Value. all of the values can be changed (as
they must with the change of prices) but you must contact the
author for the method of change.



The diamond values using "GIA.bas" are arrived at by the same
method that are used nationally. Below are wholesale values in a
listing form.

The values are in hundreds of $ and are from one supplier as of
12/27/86. And are per. ct. You must remember that Diamond prices
are often negotiated.

.01-.03Ct ROUND
P/CT VVS VS SI I1 I2 I3
D-F 5.5 5.0 4.6 3.9 3.4 2.3
F-H 5.1 4.7 4.4 3.5 3.1 2.1
H-I 4.7 4.5 4.2 3.2 2.8 1.8
I-K 4.4 4.0 3.6 2.9 2.3 1.6

.04-.07Ct ROUND
P/CT VVS VS SI I1 I2 I3
D-F 5.4 5.0 4.6 4.1 3.5 2.5
F-H 5.0 4.6 4.4 3.6 3.2 2.3
H-I 4.6 4.4 4.2 3.3 2.9 2.0
I-K 4.4 4.0 3.7 3.0 2.5 1.8

.08-.14Ct ROUND
P/CT VVS VS SI I1 I2 I3
D-F 6.0 5.5 4.9 4.5 3.8 2.8
F-H 5.5 5.0 4.6 4.0 3.5 2.5
H-I 5.1 4.7 4.4 3.6 3.2 2.2
I-K 4.6 4.2 4.0 3.3 2.8 2.0

.15-.17Ct ROUND
P/CT VVS VS SI I1 I2 I3
D-F 6.8 6.2 5.4 4.9 4.0 3.0
F-H 6.2 5.8 5.2 4.6 3.7 2.7
H-I 5.8 5.3 4.9 4.2 3.4 2.5
I-K 5.5 5.2 4.6 3.7 3.0 2.3






.18-.22Ct ROUND
P/CT VVS VS SI I1 I2 I3
D-F 11.0 8.5 7.0 6.0 5.5 4.0
F-H 9.0 7.5 6.5 5.7 5.0 3.6
H-I 8.0 6.8 6.0 5.2 4.5 3.2
I-K 6.8 6.0 5.5 4.8 4.0 2.8

.23-.29Ct ROUND
P/CT VVS VS SI I1 I2 I3
D-F 14.5 12.0 8.5 7.0 6.0 5.0
F-H 12.0 10.0 8.2 6.5 5.5 4.5
H-I 10.0 9.0 7.5 6.0 5.0 4.0
I-K 9.0 8.0 7.0 5.5 4.5 3.5

.30-.37Ct ROUND
RND IF VV1 VV2 VS1 VS2 SI1 SI2
D 23 21 20 19 17 14 13
E 21 20 19 18 16 13 12
F 20 19 18 17 15 12 11
G 19 18 17 16 14 11 10
H 17 16 15 14 12 10 9
I 14 13 12 11 10 9 8
J 13 12 11 10 9 8 7
K 11 10 9 9 8 7 6
L 9 8 8 7 7 6 6
M 8 7 7 6 6 5 5

.38-.45CT ROUND
RND IF VV1 VV2 VS1 VS2 SI1 SI2
D 28 25 23 20 19 15 14
E 25 23 21 19 17 14 13

F 23 21 19 18 16 13 12
G 21 19 18 17 15 12 11 example: .38 ct. VS1 H=15
H 19 18 17 15 14 11 10 15=$1,500 per ct.
I 16 15 14 13 12 10 9 1,500 x .38 = $570 per stone
J 15 14 13 12 11 9 8
K 14 13 12 11 10 8 8
L 11 10 10 9 8 7 7
M 9 8 8 7 7 6 6

.46-.49CT
RND IF VV1 VV2 VS1 VS2 SI1 SI2
D 32 27 25 23 20 19 17
E 27 25 23 20 19 18 16
F 25 23 21 19 18 17 15
G 23 21 19 18 17 15 14
H 21 19 18 17 15 14 13
I 18 16 15 14 13 12 11
J 16 15 14 13 12 11 10
K 15 14 13 12 11 10 9
L 12 11 11 10 9 8 8
M 10 9 9 8 8 7 7

.50-.69CT
RND IF VV1 VV2 VS1 VS2 SI1 SI2
D 52 38 33 29 24 22 20
E 38 33 31 27 23 21 19
F 33 31 29 25 22 20 18
G 31 29 25 23 21 19 17
H 29 25 23 21 20 18 16
I 24 22 21 19 17 16 14
J 20 18 17 16 15 14 12
K 16 15 14 13 13 12 10
L 14 13 12 11 10 9 9
M 11 10 10 9 9 8 8

.70-.89CT
RND IF VV1 VV2 VS1 VS2 SI1 SI2
D 62 42 38 34 30 25 23
E 42 38 35 31 28 24 22
F 38 35 32 28 26 23 21
G 35 32 28 26 24 22 20
H 32 28 26 24 22 20 18
I 27 24 23 21 20 18 16
J 22 21 20 19 18 16 14
K 19 18 17 16 15 14 12
L 15 14 14 13 12 11 10
M 14 13 12 11 11 10 9

.90-.95CT
RND IF VV1 VV2 VS1 VS2 SI1 SI2
D 70 52 45 38 34 29 25
E 52 45 40 34 32 27 24
F 45 40 35 32 30 25 23
G 40 35 32 30 27 24 22
H 35 32 30 27 25 22 20
I 30 27 25 24 22 20 18
J 25 23 22 21 20 18 16
K 21 20 19 18 17 15 14
L 17 16 15 14 13 12 11
M 15 14 13 12 12 11 10

1.00-1.90Ct
RND IF VV1 VV2 VS1 VS2 SI1 SI2
D 160 98 78 56 50 40 32
E 98 78 65 50 45 36 30
F 78 65 55 45 40 33 28
G 65 55 47 40 36 30 26
H 55 47 40 35 31 28 25
I 39 36 33 30 28 26 23
J 32 31 29 26 25 24 21
K 26 25 24 23 22 21 20
L 22 20 19 18 18 17 16
M 17 16 15 14 14 13 12

3.00-3.90Ct
RND IF VV1 VV2 VS1 VS2 SI1 SI2
D 250 190 145 115 100 85 68
E 190 145 125 105 95 80 64
F 145 125 107 95 86 75 60
G 125 107 95 87 80 70 56
H 107 95 87 80 70 60 52
I 80 75 71 65 59 51 45
J 69 65 60 56 50 45 40
K 55 52 50 47 43 39 36
L 42 40 38 35 32 30 28
M 35 31 29 27 25 23 21

4.00-4.90Ct
RND IF VV1 VV2 VS1 VS2 SI1 SI2
D 270 200 155 125 105 90 75
E 200 155 130 115 96 85 70
F 155 130 115 105 91 80 66
G 130 115 105 95 85 75 63
H 115 105 95 85 76 67 58
I 86 80 75 70 65 57 50
J 75 70 65 60 55 49 44
K 60 57 54 50 46 42 39
L 44 42 40 38 35 32 30
M 36 32 30 28 26 24 22

5.00-5.90Ct
ROUND VS1 VS2 SI1 SI2 I1 I2 I3
D 160 135 115 92 60 35 20
E 140 125 108 86 55 33 20
F 130 120 100 80 52 31 20
G 120 105 90 76 48 29 19
H 105 95 80 70 45 27 18
I 85 78 70 60 40 25 17
J 69 62 57 52 35 24 16
K 56 52 48 45 30 22 16
L 42 39 36 35 25 20 15
M 32 30 28 26 21 18 14

PRICES FOR FANCY SHAPES
USE A CONVERSION SCALE
FROM ROUNDS TO FANCY SHAPES.
PEAR : -20 TO -35% OF ROUND
MARQUISE: -10 TO -25% OF ROUND
OVAL : -20 TO -40% OF ROUND
EMERALD : -30 TO -50% OF ROUND
HEART : -35 TO -55% OF ROUND
LARGE FANCIES OVER TEN CT. ARE OFTEN PRICED THE SAME AS ROUNDS.



Florida Professional Appraisers in no way will be responsible for
any errors or omissions in this program, nor any errors in its
application. In fact we flatly state there are errors, and the
output (values) should always be checked. Any errors, other than
Dollar Values, should be brought to our attention.


Robert J. Williams GG, MPA

Now for a walk through the colored stone section. Lets assume
that you have a green faceted stone, further, you have no
equipment with which to make any identification, other than
magnification.

Select "Listing of colored faceted stones by color" number "0" on
the main menu. You will then be offered the colored stone menu.

Examine your green stone, it is transparent, so pick "Green
Transparent" from the menu # 5. you will then be given a listing
of all green transparent gemstones usually found in the gem trade
and some other not so usual listings.

Now admittedly you have a difficult job of making an
identification without knowing hardness, refractive Index, or
specific gravity, but you can with the help of these tables make
an intelligent guess.

To start, this gemstone is set in a ring which shows much wear.
After examining the stone you find evidence of scratches, or
chips, and the facet junctions are all very abraded. The prongs
holding the stone are worn. By this we will assume the stone is a
soft one that has not withstood years of hitting, banging and
abuse. This lets out all of the hard stones, and leaves you with
a hardness of 7 or less, You have now eliminated 3/4 of the
selection. (Those of you out there that want to argue that this
isn't very scientific, you are right, so go get educated, and buy
some equipment.)

Now using your magnification you re examine the stone in good
light, you look at the bottom of the stone through the table
(top) you might think you have double vision because the facet
junctions all appear to be doubled, indicating double refraction
with the indices far apart. This doubling effect plus low
hardness leaves Peridot and natural Zircon. After reading the
text suggested you could then make an educated guess that the
stone was a green Zircon. (In this text it will describe that
abraded facet junctions are a characteristic of Zircon)

You can now go back to the main menu and select "Colored stone
values" #9

You will now be given the prices, asked by wholesalers, for
colored gemstones. You will be given the lowest prices for
"commercial" goods to the high for "investment" stones. Keep in
mind most jewelry is set with commercial grade or slightly
higher, the dealer might say "this is our best" but that doesn't
mean that it is "the" best. The avg. price listed is the avg.
price most offered, that is, goods most readily available at the
time. Colored stones are sold on a "all the traffic can bear"
basis, and the prices fluctuate wildly at times. Stones offered
at the same price per ct. by different wholesalers might vary a
lot in quality or color. A demand for a popular stone will send
prices for that stone soaring, while a stone, not popular at the
time, will plummet in price.

Remembering that your stone needs to be repolished and was in all
likely hood a commercial quality stone to begin with, pick out a
price. These prices are per. ct.

Now go back to the main menu and select "colored stone size to
weight #8

Here you will pick Zircon # 8, and after measuring it with a mm
scale input the measurements in mm. The program will then give
you the weight of the stone in cts.

Multiply this (ex. .50 ct) times the value you selected (ex.
$15.00 per ct.) or 15 x .5 = $ 7.50 for the stone, wholesale. An
old worn half ct. Zircon isn't worth much, is it ?

The opinions offered here are just that, opinions, no more or no
less, but most of what you learn, was someones opinion at one
time. I hope this program is a help or at least stimulates your
thought process and makes you more eager to learn more about the
world of Gemology.

Robert J. Williams, GG







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