To read the json.bz2 files you can use the following code in python:

------------------------------------
#!/usr/bin/env python

import json, bz2
from pymatgen.entries.computed_entries import ComputedStructureEntry

with bz2.open("garnets.json.bz2") as fh:
  data = json.loads(fh.read().decode('utf-8'))

entries = [ComputedStructureEntry.from_dict(i) for i in data["entries"]]

print("Found " + str(len(entries)) + " entries")
print("\nEntry:\n", entries[0])
print("\nStructure:\n", entries[0].structure)

------------------------------------
Output:

Found 15742 entries

Entry: None ComputedStructureEntry - Ac48 Ag12 H20 (Ac12Ag3H5)
Energy (Uncorrected)     = -312.1258 eV (-3.9016  eV/atom)
Correction               = -0.0000   eV (-0.0000  eV/atom)
Energy (Final)           = -312.1259 eV (-3.9016  eV/atom)
Energy Adjustments:
  Manual energy adjustment: -0.0000   eV (-0.0000  eV/atom)
Parameters:
Data:
  mat_id                 = agm001254430
  prototype_id           = A3B5C12_37_spg230
  location               = cgat_prot/A3B5C12_prot1_spg230/runs/batch-002/H/H5Ag3Ac12/xxx_02p-00_agm001254430_spg230
  formula                = Ac12Ag3H5
  elements               = ['Ag', 'H', 'Ac']
  spg                    = 230
  nsites                 = 80
  stress                 = [[2.0345, 0.0, 0.0], [0.0, 2.0345, 0.0], [0.0, 0.0, 2.0345]]
  energy_total           = -312.12584145
  total_mag              = -0.0003234
  band_gap_ind           = 0.0131
  band_gap_dir           = 0.0865
  dos_ef                 = 78.46667
  energy_corrected       = -312.12585
  e_above_hull           = 0.13003096
  e_form                 = -0.19915126
  e_phase_separation     = 0.13003096
  decomposition          =  AcAg  Ac  AcH2 

Structure: Full Formula (Ac48 Ag12 H20)
Reduced Formula: Ac12Ag3H5
abc   :  14.778497  14.778497  14.778497
angles: 109.471221 109.471221 109.471221
Sites (80)
  #  SP           a         b         c    charge  forces                                     magmom
---  ----  --------  --------  --------  --------  ---------------------------------------  --------
  0  Ag    0.75      0.375     0.125        9.538  [-0.0, -0.0, 0.0]                              -0
  1  Ag    0.875     0.75      0.125        9.538  [-0.0, -0.0, 0.0]                              -0
  2  Ag    0.375     0.75      0.625        9.538  [-0.0, -0.0, 0.0]                              -0
  3  Ag    0.25      0.125     0.375        9.538  [-0.0, -0.0, 0.0]                              -0
  4  Ag    0.875     0.125     0.25         9.538  [-0.0, -0.0, 0.0]                              -0
  5  Ag    0.375     0.625     0.25         9.538  [-0.0, -0.0, 0.0]                              -0
  6  Ag    0.625     0.375     0.75         9.538  [-0.0, -0.0, 0.0]                              -0
  7  Ag    0.125     0.875     0.75         9.538  [-0.0, -0.0, 0.0]                              -0
  8  Ag    0.75      0.875     0.625        9.538  [-0.0, -0.0, 0.0]                              -0
  9  Ag    0.625     0.25      0.375        9.538  [-0.0, -0.0, 0.0]                              -0
 10  Ag    0.125     0.25      0.875        9.538  [-0.0, -0.0, 0.0]                              -0
 11  Ag    0.25      0.625     0.875        9.538  [-0.0, -0.0, 0.0]                              -0
 12  H     0.125     0.375     0.25         0.565  [-0.0, -0.0, 0.0]                               0
 13  H     0         0.5       0            0.488  [-0.0, -0.0, 0.0]                               0
 14  H     0         0         0            0.488  [-0.0, -0.0, 0.0]                               0
 15  H     0.375     0.25      0.125        0.565  [-0.0, -0.0, 0.0]                               0
 16  H     0.5       0         0.5          0.488  [-0.0, -0.0, 0.0]                               0
 17  H     0.5       0.5       0            0.488  [-0.0, -0.0, 0.0]                               0
 18  H     0.125     0.75      0.375        0.565  [-0.0, -0.0, 0.0]                               0
 19  H     0.75      0.125     0.875        0.565  [-0.0, -0.0, 0.0]                               0
 20  H     0.75      0.625     0.375        0.565  [-0.0, -0.0, 0.0]                               0
 21  H     0.375     0.125     0.75         0.565  [-0.0, -0.0, 0.0]                               0
 22  H     0.625     0.875     0.25         0.565  [-0.0, -0.0, 0.0]                               0
 23  H     0.5       0.5       0.5          0.488  [-0.0, -0.0, 0.0]                               0
 24  H     0.5       0         0            0.488  [-0.0, -0.0, 0.0]                               0
 25  H     0         0         0.5          0.488  [-0.0, -0.0, 0.0]                               0
 26  H     0.25      0.375     0.625        0.565  [-0.0, -0.0, 0.0]                               0
 27  H     0.25      0.875     0.125        0.565  [-0.0, -0.0, 0.0]                               0
 28  H     0         0.5       0.5          0.488  [-0.0, -0.0, 0.0]                               0
 29  H     0.875     0.25      0.625        0.565  [-0.0, -0.0, 0.0]                               0
 30  H     0.625     0.75      0.875        0.565  [-0.0, -0.0, 0.0]                               0
 31  H     0.875     0.625     0.75         0.565  [-0.0, -0.0, 0.0]                               0
 32  Ac    0.710271  0.113014  0.018819     8.27   [0.00106111, 0.00508306, -0.00889708]          -0
 33  Ac    0.308548  0.518819  0.405805     8.27   [-0.00106111, -0.00516357, -0.0088506]         -0
 34  Ac    0.981181  0.386986  0.289729     8.27   [0.01001432, -0.00116731, 0.00211479]          -0
 35  Ac    0.518819  0.210271  0.113014     8.27   [-0.01001432, -0.00241512, -4.648e-05]         -0
 36  Ac    0.597257  0.710271  0.691452     8.27   [-0.00443866, -0.00635771, 0.00678229]         -0
 37  Ac    0.981181  0.594195  0.191452     8.27   [0.00451455, 0.00630404, 0.00678229]           -0
 38  Ac    0.308548  0.789729  0.402743     8.27   [-0.01001432, 0.00124781, 0.00206832]          -0
 39  Ac    0.094195  0.902743  0.113014     8.27   [0.01001432, 0.00241512, -4.648e-05]           -0
 40  Ac    0.594195  0.981181  0.691452     8.27   [0.00443866, 0.00635771, 0.00678229]           -0
 41  Ac    0.710271  0.597257  0.191452     8.27   [-0.00451455, -0.00630404, 0.00678229]         -0
 42  Ac    0.789729  0.481181  0.386986     8.27   [-0.00106111, 0.01024663, 4.648e-05]           -0
 43  Ac    0.808548  0.905805  0.018819     8.27   [-0.00106111, -0.00508306, -0.00889708]        -0
 44  Ac    0.113014  0.710271  0.518819     8.27   [0.00443866, 0.00269478, -0.00889708]          -0
 45  Ac    0.386986  0.405805  0.097257     8.27   [0.00451455, -0.00902565, -0.00206832]         -0
 46  Ac    0.097257  0.905805  0.386986     8.27   [0.00106111, -0.01024663, 4.648e-05]           -0
 47  Ac    0.402743  0.113014  0.594195     8.27   [-0.00106111, -0.00516357, 0.0088506]          -0
 48  Ac    0.097257  0.191452  0.210271     8.27   [-0.00443866, 0.00905249, -0.00211479]         -0
 49  Ac    0.481181  0.691452  0.094195     8.27   [0.00451455, 0.00272161, 0.0088506]            -0
 50  Ac    0.808548  0.902743  0.289729     8.27   [-0.01001432, 0.00116731, 0.00211479]          -0
 51  Ac    0.113014  0.402743  0.094195     8.27   [-0.00451455, -0.00272161, 0.0088506]          -0
 52  Ac    0.386986  0.981181  0.789729     8.27   [-0.00443866, 0.00905249, 0.00211479]          -0
 53  Ac    0.594195  0.613014  0.402743     8.27   [0.01001432, -0.00124781, 0.00206832]          -0
 54  Ac    0.905805  0.808548  0.518819     8.27   [-0.00443866, -0.00269478, -0.00889708]        -0
 55  Ac    0.789729  0.308548  0.902743     8.27   [0.00451455, -0.00902565, 0.00206832]          -0
 56  Ac    0.405805  0.386986  0.597257     8.27   [-0.01001432, 0.00124781, -0.00206832]         -0
 57  Ac    0.094195  0.191452  0.481181     8.27   [0.00443866, 0.00269478, 0.00889708]           -0
 58  Ac    0.210271  0.691452  0.097257     8.27   [-0.00451455, 0.00902565, -0.00206832]         -0
 59  Ac    0.191452  0.097257  0.710271     8.27   [0.01001432, -0.00116731, -0.00211479]         -0
 60  Ac    0.613014  0.018819  0.210271     8.27   [0.00443866, -0.00905249, -0.00211479]         -0
 61  Ac    0.886986  0.597257  0.905805     8.27   [0.00451455, 0.00272161, -0.0088506]           -0
 62  Ac    0.518819  0.308548  0.905805     8.27   [-0.00451455, -0.00272161, -0.0088506]         -0
 63  Ac    0.597257  0.886986  0.405805     8.27   [0.00106111, 0.00516357, -0.0088506]           -0
 64  Ac    0.902743  0.808548  0.789729     8.27   [0.00443866, -0.00905249, 0.00211479]          -0
 65  Ac    0.902743  0.094195  0.613014     8.27   [-0.00106111, 0.01024663, -4.648e-05]          -0
 66  Ac    0.886986  0.289729  0.481181     8.27   [-0.00443866, -0.00269478, 0.00889708]         -0
 67  Ac    0.191452  0.094195  0.981181     8.27   [0.00106111, 0.00508306, 0.00889708]           -0
 68  Ac    0.613014  0.594195  0.902743     8.27   [-0.00451455, 0.00902565, 0.00206832]          -0
 69  Ac    0.405805  0.018819  0.308548     8.27   [-0.00443866, -0.00635771, -0.00678229]        -0
 70  Ac    0.289729  0.402743  0.808548     8.27   [0.00451455, 0.00630404, -0.00678229]          -0
 71  Ac    0.210271  0.518819  0.613014     8.27   [0.00106111, -0.01024663, -4.648e-05]          -0
 72  Ac    0.905805  0.097257  0.886986     8.27   [-0.01001432, -0.00241512, 4.648e-05]          -0
 73  Ac    0.691452  0.210271  0.597257     8.27   [0.01001432, -0.00124781, -0.00206832]         -0
 74  Ac    0.481181  0.789729  0.886986     8.27   [0.01001432, 0.00241512, 4.648e-05]            -0
 75  Ac    0.018819  0.405805  0.808548     8.27   [-0.00451455, -0.00630404, -0.00678229]        -0
 76  Ac    0.402743  0.289729  0.308548     8.27   [0.00443866, 0.00635771, -0.00678229]          -0
 77  Ac    0.018819  0.613014  0.710271     8.27   [-0.01001432, 0.00116731, -0.00211479]         -0
 78  Ac    0.691452  0.481181  0.594195     8.27   [0.00106111, 0.00516357, 0.0088506]            -0
 79  Ac    0.289729  0.886986  0.981181     8.27   [-0.00106111, -0.00508306, 0.00889708]         -0


------------------------------------
List of POTCARs used:

Ac: PAW_PBE Ac 06Sep2000
Ag: PAW_PBE Ag 06Sep2000
Al: PAW_PBE Al 04Jan2001
As: PAW_PBE As 06Sep2000
Au: PAW_PBE Au 06Sep2000
B: PAW_PBE B 06Sep2000
Ba: PAW_PBE Ba_sv 06Sep2000
Be: PAW_PBE Be_sv 06Sep2000
Bi: PAW_PBE Bi 08Apr2002
Br: PAW_PBE Br 06Sep2000
C: PAW_PBE C 08Apr2002
Ca: PAW_PBE Ca_sv 06Sep2000
Cd: PAW_PBE Cd 06Sep2000
Ce: PAW_PBE Ce 28Sep2000
Cl: PAW_PBE Cl 17Jan2003
Co: PAW_PBE Co 06Sep2000
Cr: PAW_PBE Cr_pv 07Sep2000
Cs: PAW_PBE Cs_sv 08Apr2002
Cu: PAW_PBE Cu_pv 06Sep2000
Dy: PAW_PBE Dy_3 06Sep2000
Er: PAW_PBE Er_3 06Sep2000
Eu: PAW_PBE Eu 08Apr2002
F: PAW_PBE F 08Apr2002
Fe: PAW_PBE Fe_pv 06Sep2000
Ga: PAW_PBE Ga_d 06Sep2000
Gd: PAW_PBE Gd 08Apr2002
Ge: PAW_PBE Ge_d 06Sep2000
H: PAW_PBE H 15Jun2001
Hf: PAW_PBE Hf_pv 06Sep2000
Hg: PAW_PBE Hg 06Sep2000
Ho: PAW_PBE Ho_3 06Sep2000
I: PAW_PBE I 08Apr2002
In: PAW_PBE In_d 06Sep2000
Ir: PAW_PBE Ir 06Sep2000
K: PAW_PBE K_sv 06Sep2000
La: PAW_PBE La 06Sep2000
Li: PAW_PBE Li_sv 23Jan2001
Lu: PAW_PBE Lu_3 06Sep2000
Mg: PAW_PBE Mg_pv 06Sep2000
Mn: PAW_PBE Mn_pv 07Sep2000
Mo: PAW_PBE Mo_pv 08Apr2002
N: PAW_PBE N 08Apr2002
Na: PAW_PBE Na_pv 05Jan2001
Nb: PAW_PBE Nb_pv 08Apr2002
Nd: PAW_PBE Nd_3 06Sep2000
Ni: PAW_PBE Ni_pv 06Sep2000
Np: PAW_PBE Np 06Sep2000
O: PAW_PBE O 08Apr2002
Os: PAW_PBE Os_pv 20Jan2003
P: PAW_PBE P 17Jan2003
Pa: PAW_PBE Pa 07Sep2000
Pb: PAW_PBE Pb_d 06Sep2000
Pd: PAW_PBE Pd 05Jan2001
Pm: PAW_PBE Pm_3 07Sep2000
Pr: PAW_PBE Pr_3 07Sep2000
Pt: PAW_PBE Pt 05Jan2001
Pu: PAW_PBE Pu 06Sep2000
Rb: PAW_PBE Rb_sv 06Sep2000
Re: PAW_PBE Re_pv 06Sep2000
Rh: PAW_PBE Rh_pv 06Sep2000
Ru: PAW_PBE Ru_pv 06Sep2000
S: PAW_PBE S 17Jan2003
Sb: PAW_PBE Sb 06Sep2000
Sc: PAW_PBE Sc_sv 07Sep2000
Se: PAW_PBE Se 06Sep2000
Si: PAW_PBE Si 05Jan2001
Sm: PAW_PBE Sm_3 07Sep2000
Sn: PAW_PBE Sn_d 06Sep2000
Sr: PAW_PBE Sr_sv 07Sep2000
Ta: PAW_PBE Ta_pv 07Sep2000
Tb: PAW_PBE Tb_3 06Sep2000
Tc: PAW_PBE Tc_pv 06Sep2000
Te: PAW_PBE Te 08Apr2002
Th: PAW_PBE Th 07Sep2000
Ti: PAW_PBE Ti_pv 07Sep2000
Tl: PAW_PBE Tl_d 06Sep2000
Tm: PAW_PBE Tm_3 20Jan2003
U: PAW_PBE U 06Sep2000
V: PAW_PBE V_sv 07Sep2000
W: PAW_PBE W_pv 06Sep2000
Y: PAW_PBE Y_sv 06Sep2000
Yb: PAW_PBE Yb 24Feb2003
Zn: PAW_PBE Zn 06Sep2000
Zr: PAW_PBE Zr_sv 07Sep2000