Apatite

**Combinations on crystals of apatite**
	Forms	Illustrations or authority
1	m, x. The almost universal type at Franklin	Figure 188
2	m, c, s. Trotter mine	Koenig
3	c, m, r, x, y, s. Parker shaft	Figure 189

Habit
Apatite occurs generally in rather rough prismatic crystals, the largest 4 inches long and 1 inch in diameter. The color is commonly green or bluish-green, ranging to gray and brown. Some of the crystals are glassy and almost transparent, but most of them are opaque.

Figure 188 Simple crystal of apatite of the common type at Franklin, showing the forms m(1010), and x(1011).
	Figure 189 One end of a more complex crystal of apatite showing the forms c(0001), m(1010), r(1012), x(1011), y(2021), and s(1121). Parker shaft.

Composition
Apatite is calcium fluophosphate. The Franklin apatite contains little or no chlorine.

**Analysis of apatite**
	1	2		3
P₂O₅	39.59	0.279		3 x 0.093
CaO	46.64	0.832
MnO	1.35	0.019	0.851*	9 x 0.095
ZnO	0.03
Ca	3.57	0.089		1 x 0.089
F	3.37	0.177
Cl	0.04	0.001	0.178†	2 x 0.089
Al₂O₃	0.56
Fe₂O₃	0.77
CaCO₃	2.82
H₂O	0.52

	99.26

[* Figure reflects 0.832 + 0.019 values shown.]

[† Figure reflects 0.177 + 0.001 values shown.]

1. Average of two analyses of light apple-green crystals embedded in calcite, specific gravity, 3.22, Franklin. S. L. Penfield (119), analyst.

2. Molecular equivalents of the essential constituents.

3. Molecular ratio giving the formula (Ca,Mn)₃P₂O₈.CaF₂, or its equivalent, CaF(Ca,Mn)₄(PO₄)₃.

Small amounts of manganese and zinc take the place of part of the calcium, and the material analyzed has for that reason been classed as manganapatite (Dana, 146). It was, however, manifestly somewhat altered and contained nearly 2 percent of carbon dioxide; hence the manganese may have been present only as the carbonate.

All the apatite crystals embedded in the Franklin limestone appear to be free from arsenic, but all those in or associated with the ores show the presence of arsenic by qualitative tests. Some, indeed, contain more arsenate than phosphate and are described under the head of svabite. (See page 121.)

Occurrence
Apatite is found sparingly in the ore from most of the openings on Mine Hill. It has been seen associated with fowlerite, franklinite, and feldspar from the Trotter mine, in calcite from the Buckwheat mine, and in light-brown crystals embedded in hardystonite from the Parker shaft. It is found in pegmatite near contacts with limestone and in the ore body.

Apatite appears to have been relatively more abundant at Sterling Hill than at Franklin. Large crystals and columnar aggregates implanted on jeffersonite or franklinite or embedded with both in calcite were seen in several collections.

In most of the limestone quarries careful search shows the presence of small prisms of bright-green apatite in the limestone, generally associated with other metamorphic minerals. It was noted particularly at the Franklin Iron Co.'s quarry, in slender prisms, and the Losey collection contains stout, well-formed blue crystals of apatite from the limestone.


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